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chapter one

THE BIRTH OF THE NORTH AMERICAN COVERED BRIDGE

American “folk” painter Charles C. Hoffmann (c. 1820–82) painted (oil on canvas) this scene in Berks County, Pennsylvania, in 1872 of Henry Z. Van Reed’s farm, paper mill, and surroundings, including a covered bridge likely of Burr truss design. (Colonial Williamsburg Foundation)

The longest of three remaining bridges in Sullivan County, Pennsylvania, the 186-foot-long Hillsgrove Bridge was built around 1850 by Sadler Rodgers of nearby Forksville. This splendid Burr truss span was nearly lost when floods caused by Tropical Storm Lee’s 12 inches of rain in September 2011 caused a house to strike the bridge, requiring extensive renovation. As work progresses, visitors can better see the exposed trusses. (A. Chester Ong, 2012)

UTILITARIAN CROSSINGS FOR A NEW CONTINENT

Although they are commonly called “covered bridges,” the essence of such bridges is what lies beneath and is protected by the roofing and siding. The full name would more accurately be “covered wooden trussed bridges” because the last two elements—the trusses and their material, wood—are essential. While the enveloping roof and siding are critical to the survival of a trussed wooden bridge, they no more define it than our own skin, also critical to our survival, defines us as a human being. Consequently, in order to pursue a full understanding of covered bridge history and development in the United States and Canada, it is necessary to consider all wooden bridges, whether covered, uncovered, partially covered, or even those blending wood and iron.

Covered bridges as defined above are not unique to North America. Historically speaking, the covered bridges of central Europe and southern China have much longer histories than those considered here, but the North American (hereafter “American”) covered bridge appears not only to have developed independently of these older traditions but along a radically different path.

What makes this so is not the phenomenon of having covers but the nature of the wooden trusses that supported the bridges. Indeed, Chinese covered bridges (langqiao, meaning “corridor bridge”) have no trusses in the conventional sense, their support being provided beneath the deck and built to accommodate only pedestrians, animals, and small carts (Knapp, 2008). European bridges appear to have originated during medieval times, only developing into vehicular bridges after several hundred years. Their truss systems are mostly unlike those that were developed in the United States. From the beginning, American covered bridges, on the other hand, were intended for vehicular traffic such as wagons, as well as for pedestrians and animals, yet in time they came to include use by even railroad trains and canal boats. Several European countries are known to have built wooden rail bridges but mostly under American influence, while China never had covered bridges carrying trains or boats. While wooden truss bridges, covered or uncovered, did not originate in the United States, the designs that emerged of such bridges were uniquely American.

Luzerne, Switzerland’s Spreuerbrücke, spanning the River Reuss, although built in 1566 by Kaspar Meglinger, exemplifies the Medieval bridge technology of Germany, Austria, and Switzerland. Besides having a chapel midstream, there is a series of sixty-seven paintings under the roof painted between 1626 and 1635 depicting “The Dance of Death.” (Terry E. Miller, 1974)

Spanning the River Ilm in the village of Buchfart, Thuringia, Germany, this two-span bridge was built around the year 1817. Each span uses a queenpost truss with a clear span of 53 feet of a total of 123 feet. (Philip C. S. Caston, 2004)

Unidentified Austrian bridge with castle above as photographed from a moving train by the co-author’s father. (Max T. Miller, 1980)

The Santiao Bridge in Taishun County, Zhejiang Province, People’s Republic of China, straddles a rock-strewn chasm. It was built in 1843 on the site of nearby older bridges that helped link the stone-lined footpaths in this remote area. (A. Chester Ong, 2007)

Seen from beneath, the Santiao Bridge is lifted by major and minor timbers that are woven together to raise the structure some 10 meters above the streambed. (A. Chester Ong, 2007)

It is commonplace to describe “the past” as simple, uncluttered, and stress-free. We are inclined to idealize the eighteenth and nineteenth centuries as slower paced and more personal, and believe that the absence of distractions such as telephones, audio systems, computers, and traffic congestion made life more relaxing and peaceful. The European immigrants who arrived at various places on the eastern coast of North America in ever greater numbers during the seventeenth century were confronted with a relatively pristine natural environment but had enormous challenges ahead of them. Except for Indian trails, there were no roads through the vast forests or over the mountains. Even in 1837, when English civil engineer David Stevenson traveled throughout the eastern United States and published his Sketch of the Civil Engineering of North America, the American road system was deplorable. Writes Stevenson: “Road-making is a branch of engineering which has been very little cultivated in America, . . . direct[ing] their whole attention to the construction of canals, as being much better adapted to supply their wants.” And also: “The roads throughout the United States and Canada, are, from these causes not very numerous, and most of those by which I travelled were in so neglected and wretched a condition, as hardly to deserve the name of highways, being quite unfit for any vehicle but an American stage, and any pilot but an American driver. In many parts of the country, the operation of cutting a track through the forests of a sufficient width to allow vehicles to pass each other, is all that has been done towards the formation of a road” (1859: 131–2). Besides the mountains and endless forest, there were rivers and streams of all sizes, from the mighty Delaware River to minor rivulets. With or without roads, travelers had only two ways to cross these waterways: by fording or by ferry.

The old Miller Ferry crossed Alabama’s Tallapoosa River before a covered bridge was built. Its peaceful appearance belies an exceptionally violent battle fought here on March 26, 1814 when troops under General Andrew Jackson fought the Red Stick tribe of the Creek in a war for control of much of the South. Jackson’s troops, aided by a rival tribe, killed nearly 800 of the 1,000 Red Stick warriors, a tragic event memorialized in a national park. (Horseshoe Bend National Military Park)

Even as late as 1797, famed American portrait painter Charles Willson Peale warned: “Easy and safe passages over the waters of the United States are much wanted—even our post roads are deficient; often the affrighted traveller stops, and surveys the turbulent torrent that hides an unknown bottom, he hesitates—doubts whether to risk a passage or not; at last, by delay grown impatient, he with fear and trembling cautiously moves forward and perhaps arrives in safety on the opposite bank; but alas! Too frequently the rash, or fool-hardy driver, is carried down the stream, and all is lost!” (1797: iii).

Fording was only possible when water levels were low enough and the stream bed solid enough to support hooves or wagon wheels. This could change suddenly after a hard rain, making travel extremely unpredictable.

Since deeper and wider rivers, especially the broad estuaries of the great rivers approaching the sea, could never be forded, toll ferries appeared when individual proprietors found it possible for them to be economically viable. When the water level was too high, too low, too swift, or the river was frozen, ferry services usually ceased operation, leading citizens to wish for a better solution—a bridge.

Peale also commented on this matter: “Legislatures, and you men of influence in the counties of each State! Turn your attention to this important object—shorten the distance to market for the sale of the product of your lands. I offer you a cheap and easy mode of building Bridges, the principles of which are so simple, and the mechanism so easy, that any ingenious man may execute them” (p. iii).

Even then, of course, humankind already had long and extensive experience building bridges. European immigrants to America knew bridges from home and had doubtless crossed many in their lifetime. But standing there on the wooded shore of one of America’s wild and hitherto unbridged rivers, they had to determine for themselves how to get people, animals, and freight across safely. Some of the pioneers knew stone masonry and wood joinery from the “old country,” principally parts of the British Isles or one of the German-speaking areas of central Europe. Few, however, had experience building bridges.

Stone arch bridges typified the English solution to crossing rivers, but they were expensive and slow to build. Seen here is one half of a two-span bridge over the River Tees leading to the twelfth-century Barnard Castle in England’s County Durham. (Terry E. Miller, 1987)

Looking about, they had only two materials at hand: stone and timber. Europeans, particularly those from the British Isles, knew stone to be an effective material for building bridges, but such structures were costly and time-consuming to build. There were too few skilled stone masons and builders to cross more than a few of the smaller streams, and crossing major rivers was out of the question. While true that stone bridges predominated in the British Isles, Britain had mostly small streams and modest rivers to cross.

More abundant and more easily worked was wood from America’s vast forests, which were filled with old growth trees of every kind. Perhaps a few of the German speakers had seen wooden bridges in central Europe, particularly in what are now Germany, Austria, and Switzerland, but if any were experienced bridge builders, we do not know their names. Thus, the settled immigrants in the British colonies, soon to become the United States of America, had to use their own ingenuity to solve the most pressing problem that blocked transportation: learning how to build bridges.

Among them were skilled wood joiners with experience building mills, barns, and houses. Sawmills were already well established. Builders understood how to create strong frameworks of beams and how to span distances, especially for roofs. Small foundries could make nails, bolts, and straps of iron. Stone masons could build abutments and piers for bridges using patterns similar to those in houses and mills. However, bridge builders found that wooden beams alone are neither long enough nor strong enough to span more than a limited distance, requiring in most cases a series of stone piers, and the techniques for building such structures within the moving waters of a mighty river were as yet unknown.

How much American bridge builders knew about wooden bridge building in central Europe remains uncertain, but the solutions that developed in the young United States suggest Yankee ingenuity rather than a continuing tradition. If there was an American timber framing tradition, it relied on fundamental principles rather than wholly learned bridge patterns. The two principles that form the basis of virtually all bridge solutions that emerged in America are, one, the rigidity of the triangle, and two, the strength of the arch. Beyond these, there was only trial and error, experience, and common sense since scientific analysis of stress in bridge design was unknown until the middle of the nineteenth century. In fact, Civil Engineering as a named field offering training in bridge design and construction developed long after that.

An understanding of what came to be the “American covered bridge” requires, first, an understanding of the basic solution to the stream-crossing challenge—the bridge truss. Builders realized that by joining timbers into patterns consisting of little more than triangles or by creating continuous arches they could build structures rigid enough and strong enough to span great distances, eliminating the need for extra stone piers, which were obstructions to the flow of the rivers and to navigation. Although some small iron fasteners and straps were available, most of the joinery required only wooden dowels, called trunnels (“treenails”).

American craftsmen used wood arranged into rigid patterns to span rivers. Ashulot, New Hampshire’s Upper Village Bridge, built in 1864, uses Ithiel Town’s patent design from 1820 that consists of planks held together with wooden dowels, called trunnels (from “treenails”). (A. Chester Ong, 2010)

A pair of extra long trunnels pierce both pairs of lower chords and the lattice planks of Georgia’s Cromer’s Mill Bridge built in 1906 by James M. “Pink” Hunt. (A. Chester Ong, 2011)

The heavy cross beams supporting the deck of this bridge in Washington County, Pennsylvania, are hung below the lower chord from an iron eye-bar above to a nut fastener below. (A. Chester Ong, 2011)

One of many of New Hampshire’s iconic bridges, the Haverhill-Bath Bridge crosses the Ammonoosuc River in Woodsville where water cascades over both rocks and an old industrial dam. Built in 1829 by the town supervisors for about $2,400, the two-span 256-foot-long Town lattice structure carried NH 135 until 1999. An earlier restoration added massive arches and a pedestrian walkway on the upstream side. (A. Chester Ong, 2010)

The centerpiece of Sullivan County, Pennsylvania’s tiny community of Forksville (pop. 145) is its bridge over Loyalsock Creek built in 1850 by Sadler Rodgers, then only 18 years old, using the Burr truss. (A. Chester Ong, 2012)

Builders came to find endlessly creative ways of combining timbers into individually named trusses based on the triangle principle, whether combined with an arch or not. Moreover, being entrepreneurs they sought to protect as well as capitalize on their designs through the newly developed patent system, which promised an inventor a fee for the use of his design. As was typical of what many identify as the “American spirit,” designs proliferated, some becoming wildly successful, others having little or no application, and some appearing downright whimsical. What came to be called the “American covered bridge” initially was simply a “bridge,” and the story of the American covered bridge is essentially one of innovations in framing trusses.

The United States conducted its first census in 1790, ascertaining that there were slightly fewer than four million people living in what had recently been thirteen colonies, plus the districts of Kentucky, Maine, Vermont, and Tennessee. All but around 200,000 citizens were classified as “rural,” for America’s cities were then mere towns compared to what they would become. In 1790, New York City had but 33,131 people, Philadelphia only 28,522, and Boston a mere 18,320. Even with immigration, the US population would not exceed 100 million until the 1920 census. What this tells us is that relatively few people had to perform the tasks required to build the new nation, including its bridges.

Thus, the self-appointed, amateur “civil engineers” who took it upon themselves to solve the river crossing problem were forced to improvise based on common sense and experience. Having no known direct knowledge of Germanic timber bridges, they had at their disposal few documents that might provide clues. One of these was the writings of Italian architect Andrea Palladio (1508–80), the person most responsible for codifying classical architecture and designing numerous significant buildings and churches that now characterize the Italian Renaissance style. His I quattro libri dell’architettura [The Four Books of Architecture] was first published in 1570 and came to be known to the English-speaking world after an illustrated translation was published in London in 1738. In this document, Palladio described both in words and drawings four proposed wooden bridges, only one of which is known to have been built. All were simple trusses based on two of the most fundamental patterns, the kingpost and the queenpost, which are described in the next chapter. None was capable of spanning more than about 50–60 feet, however. While we can document the possible availability of Palladio’s drawings to American builders, there is no way of knowing whether they actually replicated his basic designs into their own bridges.

Two Swiss bridges and their intricate structures were known to potential engineers in places like Philadelphia and New York because numerous travelers had provided detailed diagrams, some published in the United States. The first was the immense two-span covered bridge at Schaffhausen, Switzerland, built by Hans Ulrich Grubenmann between 1756 and 1758. Originally intended to be a single span of 364 feet, the city elders insisted on two more modest but unequal spans measuring 193 and 171 feet respectively, each supported by an elaborate system of overlapping queenposts plus a system of struts reinforcing the ends. The second bridge was built in the 1760s by members of the Grubenmann family at Wettingen over the Limmat near Baden. Its 200-foot span was supported by a massive seven-layered, iron-banded, laminated arch nearly seven feet thick attached to the frame. Although not typical of American bridges then or later, at least one of eminent American builder Theodore Burr’s massive bridges, the multi-span bridge crossing the Delaware at Trenton, which took three years to build (1804–6), closely resembles the Wettingen bridge. Engravings of both Swiss bridges clearly showed them to have been covered with roofs. From references in several documents, we know that a few Americans knew the European tradition of covering wooden bridges for protection.

Andrea Palladio included plans for three truss bridges in his 1570 I quattro libri dell’architettura [The Four Books of Architecture], two reproduced here: (left) 1–15, a queenpost design, and (right) 1–16, a multiple kingpost design. (Palladio, English translation, 1738)

Now long gone, Schaffhausen, Switzerland’s famous bridge over the Rhine, was much noted by travelers and artists, here immortalized in the hand-colored etching by Johann Heinrich Bleuler (1758–1823). The 364-foot two-span bridge was built between 1756 and 1758 by Hans Ulrich Grubenmann, whose complex design involving numerous polygonal arches and various struts attracted the attention of early civil engineers. (© Trustees of the British Museum)

Although there is the possibility that America’s self-made bridge builders could have known the work of Palladio and the Grubenmann families, there is no known direct evidence to connect them to those specific designs or bridges. What is so remarkable about the nation’s first generation of bridge engineers is that they not only, as it were, had to “reinvent the wheel” but did it with an unparalleled boldness bordering on the brazen. Civil engineering historian Lee H. Nelson’s concise but definitive study, The Colossus of 1812: An American Engineering Superlative (1990), focuses on the work of four exemplary early builders and their bridges: Charles Willson Peale (1741–1827), Timothy Palmer (1751–1821), Theodore Burr (1771–1822), and Lewis Wernwag (1769–1843).

Among the first problems encountered by early bridge builders was that many of the young American towns needing bridges sat beside broad tidal rivers which often flowed deep. Some were more than a thousand feet wide, others even half a mile, and in one case, the Susquehanna in central Pennsylvania, more than a mile wide at some points. All were major impediments to transportation, trade, and urban expansion. Frances Manwaring Caulkins’ History of Norwich, Connecticut sums it up well: “. . . roads could not have been opened and rendered safe for traveling in any direction without spanning a multitude of small streams with some kind of stone-work, or with timber and plank, and these perhaps the next spring flood would sweep away. Consequently the work of building and repairing bridges was always beginning, ever going on, and never completed” (1874: 343).

Partial plan of Schaffhausen Bridge showing both trusses and cross sections. (Fletcher and Snow, 1934)

Until the French developed deep-water caisson technology during the nineteenth century, builders of multiple-span bridges had to contend with the difficult task of placing stone piers mid river, sometimes utilizing simple coffer dams, which were temporary enclosures within a stream. It was not until 1872 that James B. Eads, the builder of the Brooklyn Bridge, took out his path-breaking patent for a watertight caisson structure that greatly facilitated the construction of deep-water bridge piers. Until then, builders were only able to construct piers in relatively shallow rivers and consequently were forced into creating (or at least imagining) grandiose spans for other situations. Some early builders proposed and even built some of the most daring bridges in American history.

Thomas Pope patented his “Flying Pendent Lever Bridge” in 1807 and published plans in his 1811 A Treatise on Bridge Architecture. There he claimed (imagined) that he could build an 1,800-foot covered arch over the East River in New York City. (American Philosophical Society)

Charles Willson Peale published his proposal for a 390-foot laminated arch bridge over the Schuylkill at Market Street in Philadelphia in An Essay on Building Wooden Bridges. (Peale, 1797; reproduced in Nelson, 1990: 7)

To get an idea of their boldness, consider New York “architect and landscape gardener” Thomas Pope, who patented in 1807 his “Flying Pendent Lever Bridge,” a rainbow-like “grand parabolic arc,” which is described in detail in the last 50 pages of his 288-page A Treatise on Bridge Architecture published in New York in 1811. That same year he came to Philadelphia and exhibited a model of half of such a bridge which was, by his account, some 50 feet long and weighed 10 tons (1811: 23).

During this time, Pope proposed to build several bridges, but only that for the Lancaster-Schuylkill or Upper Ferry, the future location of a bridge by Wernwag, has survived. Presumably using a plan like his “Flying Pendent Lever Bridge,” he proposed a single span of 432 feet, 46 feet above the water, and estimated to cost $50,000 exclusive of the abutments and covering. That the city fathers ignored the proposal suggests sane leadership on their part. In a footnote in his book, Pope also noted that the specifications printed there were for a single span of 1,800 feet with a “versed sine” (arch rise) of 223 feet over the East River in New York. However mad his idea seems, Pope must be credited with being the most flamboyant bridge designer in American bridge history.

Not far behind was noted portrait painter Charles Willson Peale, who in his 1797 An Essay on Building Wooden Bridges proposed to span the Schuylkill at Market Street with a 390-foot laminated arch bridge rising 39 feet at the center. This rise, however, would have created an horrendous burden on the teams pulling the loads over this unwieldy structure. Pope and Peale wished to attempt such feats because building piers in the deep river was then impossible.

Peale’s drawings for a giant laminated wooden arch bridge show he planned to leave it uncovered. Peale was aware of the option of covering the structure, because he mentioned that bridges with covering already existed. Writes Peale: “It has been advised to make roofs to cover Bridges, and some are so constructed in America; but I conceive this to be a very unnecessary expence [sic], for if the Bridge is not wholy [sic] kept from the wet by such covering, then instead of being a benefit, the roof becomes a disadvantage, by hindering the sun and air from drying and carrying off the moisture; and moreover such high and large surfaces for the wind to act upon, would require a great addition of width in such Bridges. Yet I must acknowledge if ever such coverings are necessary, it must be in the old construction of wooden Bridges with numerous mortices [sic], which are so many deep receptacles for holding water; and it is here that they have their points of bearing, for the support of such arches are only at certain distances, and hence for the maintaining of such constructions, they are obliged to be composed of an immense weight of timber” (1797: 13–14).

Taking Peale at his word, then two things are clear: first, that wooden truss bridges with siding and roofing were in existence at least by 1797 (and probably some years earlier since he wrote this in 1797), and second, that their covering was of no significance other than as a utility. Our current obsession with covered bridges might have struck Peale as odd because he was concerned only with bridges—bridges necessarily built of wood and necessarily protected, either with pitch or weatherboarding. It goes without saying that the covering now thought to be so nostalgic and romantic had no such meanings in early America.

Peale’s observation also suggests that the type of bridge then being covered had some sort of truss because the covering protected the mortise and tenon joinery. Timbers had to be joined because they had to bear stresses both from their own weight as well as from live loads. Therefore, the main reason to cover a wooden bridge was to protect its stress-bearing trusses pinned together with mortises. Since transportation priorities probably dictated that the first bridges would span the most obstructive waterways, therefore these must have been substantial.

Ever since the publication of Richard Sanders Allen’s Covered Bridges of the Middle Atlantic States (1959), students of covered bridges have accepted his assertion that the first covered bridge in the United States was Timothy Palmer’s “Permanent Bridge” of 1801–5, which Owen Biddle covered with roof and siding only after completion of the trusses in early 1805. But Allen’s book also hid an apparent secret in full sight on page 2, that the idea of a covered bridge had been recognized as early as 1787, some eighteen years earlier. The first issue of The Columbian Magazine, published in January 1787, included a detailed drawing of a proposed bridge by an anonymous builder, presumably to cross the Schuylkill in four spans. The cutaway drawing clearly shows what was later called a “multiple kingpost truss” with additional arches that appear to rest on the lower chords and not into the abutments and piers.

The first known drawing of an American covered bridge was published in the January, 1787 issue of The Columbian Magazine. (1787: 4)

Indeed, this is exactly what was later known as a Burr truss or Burr arch after Theodore Burr. Since Burr would have been only sixteen at the time, it is highly unlikely he had anything to do with it, and besides, he was being raised in distant Torrington, Connecticut. Both roof and siding are clearly visible. Granted, there is no evidence that this exact bridge was ever built, but clearly builders already envisioned the type of bridge that became typical only twenty or so years later. The most likely reason for its not having been built is that masons had no way to build the three stone piers in the river’s deep waters.

Earliest Documented Wooden Bridges

The “covered bridge,” including Palmer’s “Permanent Bridge” of 1805, of course did not just appear out of the blue. It developed within the historical context of American bridge building, and the act of covering a bridge was simply an option chosen more and more when builders wearied of having to rebuild bridges every few years because they kept rotting and collapsing, wisely giving in to common sense. Builders resisted covering their work because some believed it trapped moisture inside or provided too much wind resistance, while others thought a cover denied the public the opportunity to be awestruck by the magnificence of their work. While true that Palmer’s great bridge over the Schuylkill was the first documented covered bridge, it was but one of Palmer’s many engineering feats. And feats they were. But Palmer was not alone. The first generation of American bridge builders included some of the boldest bridge designers and builders in American engineering history. This Hall of Fame must include at least these additional names: Colonel Enoch Hale (1743–80), Moody Spofford (1744–1828), Jacob Spofford (1755–1812), Timothy Palmer (1751–1821), William Weston (1763–1833), John Templeman, Samuel Carr, Theodore Burr (1771–1822), Lemuel Cox (1736–1806), James Finley (1756–1828), and Samuel Sewall Jr (1724–1815).

One can hardly speak of a road system during the colonial period, the sparsely populated cities being connected with an uncertain system of dirt/mud roads, sometimes “paved” with corduroy (logs), many of them private turnpikes. If bridges crossed any of the many streams and rivers, they had to have been simple structures little noted in written documents. Some that were noted were built by Lemuel Cox who, with Samuel Sewall Jr, built several pile and trestle bridges before the Revolutionary War. Their “Great Bridge” or “Sewall’s Bridge,” some 270 feet long, built in 1761, crossed the York River in what is now York, Maine.

After the war, Cox built a toll bridge 1,503 feet long linking Boston and Charlestown, which opened on June 17, 1786. The next year he built another over the Mystic River north of Cambridge, Massachusetts. His greatest pile and trestle structure, however, bridged the Charles River at West Newton with a structure 3,483 feet long and 40 feet wide that was carried on 180 wooden trestles (Allen, 1991: 11–14). Most of these included a drawspan to allow boats to pass. Caulkins’ History of Norwich, Connecticut, quoted earlier, details the innumerable bridges built in that area, few of which lasted longer than two or three years: “These early bridges, being supported mainly by heaps of stones, and studs driven into the bed of the river, could offer but slight resistance to the crushing piles of ice that came down with the released waters in the time of floods” (1874: 350).

Sewall’s Bridge, built in 1761 by Samuel Sewall Jr over the York River at York, Maine, was possibly the first American pile-driven bridge with a draw-span, some 270 feet long. It was replaced in 1934 by a new bridge of similar design. (Library of Congress, 1908)

An old log trestle built to carry a rail line running through the mountains between Santa Cruz and Felton, California. (Terry E. Miller, 2012)

Most bridge historians credit Revolutionary War hero Colonel Enoch Hale with constructing the nation’s first substantial bridge. Built in 1785, it crossed the Connecticut River far to the north of Boston and Philadelphia, at Bellow’s Falls, Vermont, where the river is narrowed by dramatic rock outcroppings. Here was a critical crossing point where the usual solution, a ferry, was not feasible. Although it was an open wooden structure, Hale’s crossing lasted an amazing fifty-five years, until 1840, when it was replaced by a substantial covered bridge, by then a typical solution. Hale’s Bellow’s Falls crossing consisted of massive beams placed vertically at key points on the rocky outcroppings, with a flat deck above supported by heavy wooden corbels running at 45 degrees from the vertical posts to the deck beams and forming what appears as a simple triangular “arch.” Considering the limited construction technology of the day, it is a wonder that mere men could place such heavy timbers within a dangerous river bed and complete such a long-lasting structure (Litwin, 1964: 13).

A possible “missing link” in American bridge history is the “Leffingwell Bridge,” named after the nearest landowner. According to Frances Manwaring Caulkins, writing originally in 1845, and quoting a newspaper article from June 20, 1764: “Leffingwell’s Bridge over Shetucket river at Norwich Landing [Connecticut] is completed. It is 124 feet in length and 28 feet above the water. Nothing is placed between the abutments, but the bridge is supported by Geometry work above, and calculated to bear a weight of 500 tons [sic]. The work is by Mr. John Bliss, one of the most curious mechanics of the age. The bridge was raised in two days and no one hurt. The former bridge [Edgerton’s bridge] was 28 days in raising” (1874: 348).

The Connecticut River, running between Vermont and New Hampshire, passes through an especially rugged gorge at Bellow’s Falls, Vermont. In 1785, Colonel Enoch Hale managed to construct a beam bridge supported by angle braces here that lasted until 1840, though no photographs of it are known. (NSPCB Archives, R. S. Allen Collection)

This scale model, believed to be John Bliss’s 1764 “Geometry Bridge,”also called Leffingwell’s Bridge, over the Shetucket River at Norwich, Connecticut, is kept at the Faith Trumbull Chapter of the Daughters of the American Revolution (DAR) house in Norwich. (Gerald Dyck)

Caulkins continues: “This bridge retained its position, and the proprietor was allowed a portion of the toll for fourteen years. But in 1777 it was much injured by floods, and the town having purchased Leffingwell’s remaining interest, united with Preston in petitioning the Legislature (May session, 1778) for leave to raise money by lottery for the erection of a new bridge. The petition was granted” (p. 348).

“Geometry bridge” suggests the use of a truss. Considering that Palladio’s work had been known after its translation into English was published in 1738, it is entirely possible that builders here and there were constructing at least modest spans, almost certainly not covered. Indeed, Caulkins later refers to a bridge standing in 1813 as “the Geometry Bridge at Chelsea” (p. 349).

The Faith Trumbull Chapter of the Daughters of the American Revolution (DAR) in Norwich possesses a large-scale wooden model of uncertain age that purports to depict the old bridge. If this is accurate, then we can be sure a “geometry bridge” was an open double polygonal arch with posts forming four panels. While polygonal arch covered bridges exist in Germany and Switzerland, they are generally more complex, suggesting that Bliss either knew something of such precedents or independently invented it. Otherwise, the Leffingwell Bridge appears to be an isolated, one-of-a-kind design.

Between Hale’s brave span of 1785 and Palmer’s fully covered “Permanent Bridge” in 1805, a mere twenty years, American bridge technology made tremendous strides thanks to a small group of incredibly savvy, bold, and self-taught “bridge carpenters.” All of the documented bridges, because they spanned major rivers, required extensive amounts of cut and sawed timber, thousands of tons of massive stone blocks, and hundreds of men, horses, and their necessarily simple tools. Additionally, every project had to be initiated with private capital because the governments of the time were not yet in the business of building roads and bridges. Risking great amounts of money to construct bridges over dangerous and wild rivers that routinely flooded with both water and ice floes each year, these early entrepreneurs appear to have lost out more often than they succeeded. In those days, investing in a bridge company was no sure way to safeguard one’s assets or increase one’s equity, and thus the bridge building business developed slowly.

Published by Ebenezer Turrell Andrews and Isaiah Thomas in The Massachusetts Magazine in 1793, “Newbury Bridge over Merrimack River” clearly shows Timothy Palmer’s Deer Island Bridge between Salisbury Point and Newbury constructed as open trusses in 1792. The left span was 113 feet long plus open trestle spans, and the right span was 160 feet, both using arch-reinforced trusses. The north span (left) was covered in 1810 and survived until 1882 while the south span (right) was replaced in 1810 by a chain suspension bridge. (Boston Athenaeum)

At least six major bridges were constructed over Massachusetts’ Merrimack River between 1792 and 1795. Three men were chiefly responsible: Moody Spofford, Jacob Spofford, and Timothy Palmer, all living in nearby towns. Of these, Palmer, of Newburyport, became the most famous, though he is said to have learned his skills from the Spoffords. Together with Jacob Spofford, Palmer first designed and built the Deer Island Bridge between Newbury and Salisbury Point, also known as the Essex Merrimack Bridge, in 1792, only seven years after Hale’s corbel-supported bridge at Bellow’s Falls. The Essex Merrimack Bridge Company was authorized on May 30, 1791, and their charter granted on January 9, 1792. Amazingly, the bridge opened in late November (one source gives November 26, another November 20) of that same year. Two historians, Laura Woodside Watkins and Richard Sanders Allen, have written brief histories of the bridge, Allen’s 1996 study contradicting Watkins’ 1961 one on several points.

The Essex Bridge crossed the river in two segments separated by Deer Island. According to an engraving and plate description published in The Massachusetts Magazine in May 1793, the bridge’s length was 1,030 feet in total. The northern segment, connecting Salisbury Point to the island, consisted of three short trestle spans, one of them a 40-foot draw, between what were likely piers of wood cribbing, completed with a trussed span of 113 feet to the island. The southern portion was mainly a trussed span of 160 feet. The engraving contradicts the description in several ways, showing the shorter trussed span with ten panels and the longer one with eight, and also not mentioning the long approach on the Newburyport side shown in the engraving. According to the drawings, the multiple kingpost trusses have arched upper and lower chords with either corbels or arches reinforcing the bridge from beneath. If accurate, the engraving suggests that Palmer had followed the basic principles of Palladio’s designs, especially that of his bridge over the Brenta River at Bassano, Italy, “at the foot of the Alps” (1738: 67–8). In December 1792, only a month after the bridge’s opening, The Massachusetts Magazine noted “The arch is deemed the largest on the continent. The whole work contains more than 6000 tons of timber. Mr. Timothy Palmer, an ingenious house wright of Newburyport, has received a medal, for the best construction of an arch.” By 1810 the southern span had deteriorated to the point that it was torn down and replaced by a novel chain suspension bridge based on the patent design of Judge James Finley of Pennsylvania and built by John Templeman of Georgetown, Maryland (now District of Columbia), and Palmer’s close associate, Samuel Carr. The north span, covered around 1810, survived until 1882. A photograph in the R. S. Allen archives shows this remaining span as a fully covered double-lane structure with one or more arches beneath the trusses and deck.

A view from the shore of Palmer’s Newbury Bridge long after being covered, showing part of the trestle and drawbridge approach. (NSPCB Archives, R. S. Allen Collection)

In 1793, two major bridges were built, but the first of them, the Middlesex-Merrimack Bridge at Lowell, Massachusetts, also called the Pawtucket Bridge, consisted of three open flat-deck spans, the eastern two braced with corbels and the longer western span supported by an arch placed beneath the deck. The designer and builder may have been Col. Loammi Baldwin (1745–1807). Reports say that it was “rebuilt” in 1795 and again in 1805.

The second was the Andover Bridge over the Merrimack built by Timothy Palmer and Moody Spofford, reportedly for 3,998 pounds, but there are no known illustrations. It was described as having three spans with wooden piers, the center span being 110 feet. Considering who built it and the length, we would assume it to have been another arched truss bridge. As in so many other cases, nature was unkind to Andover’s citizens, for the main span collapsed eight years later, on August 28, 1801, under the weight of a livestock drive. Asa Town replaced it with a bridge of three framed arches, but an ice jam destroyed most of the bridge in 1807, and the crossing was not rebuilt until some thirty years afterwards.

The following year, 1794, saw the construction of two more remarkable bridges. The lesser known Piscataqua Bridge, seven miles north of Portsmouth, New Hampshire, consisted of a hundred short spans on pile and trestle piers but having a “stupendous arc” span of 244 feet over the navigable channel of Great Bay. Considering that the builders included Timothy Palmer, we can surmise that the arched span resembled those built earlier, but its length, if correct, would be remarkable and unprecedented. If correct, then Palmer’s span approached the bold dimensions of some bridges proposed but not built by Pope and Peale.

The bridge from Haverhill to Bradford, Massachusetts, over the Merrimack is probably the best understood of Palmer’s great bridges since it lasted until 1875 when it finally had to be demolished. Although there are numerous photos of the structure taken long after it had been covered, according to Timothy Dwight, President of Yale University and author of Travels in New-England and New-York (1821–2) who visited the bridge twice, in 1796 and 1812, the bridge underwent considerable “rebuilding” or “remodeling” in 1808 and 1825, the earlier one supervised by Palmer himself. Because the piers were so massive, each containing 4,500 tons of stone, it is unlikely the remodeling changed the span lengths, each of the three being 182 feet. In addition, the bridge was double lane, each lane being 15.5 feet wide, and the arch, located beneath the trusses, rose 8 feet. Wright related that Palmer, along with co-builder Moody Spofford, first demonstrated the bridge’s strength with a 10-foot model that allegedly held eleven men weighing together 1,600 pounds. Between the Bradford shore and the third span stood a 30-foot drawbridge. Dwight reports that decay had set in by 1812 on his second visit, and that the arches had been removed. Since he does not mention the bridge as now covered, we presume that covering came later, perhaps as late as 1825. Surviving photos, however, show that the arches had been restored and an uncovered walkway added. That Palmer and Spofford could have built such a magnificent bridge with such great spans in 1794 demonstrates how advanced bridge building had become by that time.

Although there are photographs of the Rocks Village Bridge over the Merrimack between West Newbury and East Haverhill, these include the 1828 Town lattice replacements for two of the original six built by Palmer and Moody Spofford in 1795 and partially rebuilt by them around 1812. The original bridge, which opened on November 26, 1795 and was described as the “longest on the river,” is said to have been nearly 1,000 feet long with six arched trusses. Palmer’s rebuilding, around 1812, only survived until 1818 when ice and high water destroyed part of it. The crossing then remained incomplete for ten years.

Although Palmer’s early bridges all crossed the Merrimack River in Massachusetts, his fame spread, and in 1796 he was commissioned to build what was later known as the Chain Bridge over the Potomac River two miles above Georgetown at Little Falls. Chartered in 1794, the company hired Palmer and Jacob Spofford to build a multi-span bridge with a roadway that ascended and descended over each arched truss span. The longest was described as being 130 feet long with two additional spans that were shorter. Benjamin Henry Latrobe (1764–1820), a traveler from England, said it had been “framed in New England of white pine & brought hither by water,” suggesting that it was prefabricated, probably in Massachusetts, and shipped by water (1905). After its opening in 1797, it is said that George Washington routinely crossed it on the way to Mount Vernon. A critical French visitor wrote that it was “disgusting in its heaviness, having an immense quantity of timber and iron wasted on it” (La Rochefoucauld-Liancourt and Neuman, 1799). Not knowing that the bridge had already decayed and collapsed in 1804, Palmer wrote in 1806 that “the bridge I built over the Potomac at Georgetown in 1796 is not safe for heavy teams to pass over” (quoted in Peters, 1815). The Georgetown Bridge Company, owner of the crossing, duplicated the original, but only six months later a spring freshet destroyed the bridge. The third bridge, a chain suspension bridge, which gave the crossing its name, was built by James Finley (1756–1828) of Pennsylvania and John Templeman of Georgetown in 1807–8.

In 1794, Palmer and Moody Spofford built this great bridge from Haverhill to Bradford, Massachusetts, over the Merrimack River. Each of its three spans was 182 feet long, over 30 feet wide, plus a short drawspan that allowed ships to pass. This photograph, taken during demolition in 1875, shows something of its structure. (NSPCB Archives, R. S. Allen Collection)

Left uncovered until about 1825, the Haverhill Bridge received its open walkway on one side at a later date. (NSPCB Archives, R. S. Allen Collection)

A view of Palmer and Spofford’s Haverhill Bridge in the winter when the bridge’s floor would have been paved with snow to allow sleighs to pass. (NSPCB Archives, R. S. Allen Collection)

Originally built in 1795 by Palmer and Moody Spofford, the Rocks Village Bridge over the Merrimack, nearly 1,000 feet in length, lost two spans to a flood in 1818, these not being replaced until 1828. In this photo of the successor spans—none, apparently, the originals—an open turning bridge allows a sailing ship to pass. (NSPCB Archives, George B. Pease Collection)

Although more and more bridges were being built by this time, two stand out. One was a two-span arched bridge built uncovered by Captain Boynton between May 5 and November 21, 1797 over the Kennebec River at Augusta, Maine, for $27,000. The eastern span collapsed on June 23, 1816, but a new bridge was not built until 1818 when the western span was also replaced. The second bridge, the Lansingburgh-Waterford Union Bridge, a 800-foot-long four-span bridge over the Hudson River in New York State, is the first known work of Theodore Burr (see further discussion below). If Palmer was bold, Burr was brazen, for each arched span was around 200 feet long, with 18-foot-high arches, and two roadways. Opened on December 3, 1804, this was the first bridge over the Hudson and remained uncovered until 1814. When it burned on July 10, 1909, it was then the oldest wooden trussed bridge in the country.

By 1804, then, several builders had brought the science of wooden bridge construction to a surprisingly sophisticated level with many remarkable bridges and daringly long spans. None of them is known to have been covered with roof and siding, Peale’s assertion notwithstanding. Clearly, though, builders knew about covering bridges, but there was not yet general agreement on the benefits. None could deny, however, that in spite of tight joints, paint, or pitch, these glorious arches and trusses deteriorated if left open to the elements. The next step would lead to the creation of the first documented covered bridge in the United States.

Bridge historian Francis E. Griggs Jr’s concluding remark on the significance of Timothy Palmer’s Permanent Bridge in Philadelphia, the country’s first known covered bridge, sounds a bit hyperbolic, but within the historical context up to that point, he is likely correct: “. . . there is no doubt that Palmer had designed and built one of the most significant bridges in the world and maybe the most advanced wooden bridge ever” (2009: 516). Additionally, thanks to its location and the attention it garnered both in the United States and Europe, there is voluminous documentation, including diagrams, paintings, letters, and contracts, but alas, no photographs. Palmer, however, who later partially rebuilt and covered his 1792 Salisbury span over the Merrimack in 1807, wrote in a letter: “Last summer, I rebuilt one of the Arches; the span of which is 113 ft and is on the same principle with your Bridge” (Griggs, 2009: 513). Since there are photos of this bridge, we can more easily picture the much longer but more artistically finished Permanent Bridge.

Boston and Philadelphia were doubtless the two most important cities in the English Colonies at the time of the Revolution. During the revolutionary period, Philadelphia was the site for the signing of the Declaration of Independence, the writing of the Constitution, and the convening of the Continental Congresses. Following American independence, which was declared on July 4, 1776, and the final surrender of the British to General George Washington at Yorktown on October 19, 1781, Philadelphia continued to play a critical role as the seat of new national government, and from 1790 to 1800 it served as the temporary capital of the young United States while Washington, DC, was being built. In spite of a deadly outbreak of yellow fever, the city prospered, but its growth and communication with all points east were stymied by the Schuylkill River and the limitations of the ferry service first established in 1723. A movement to build a bridge on High Street, later called Market Street, began in 1750, but for numerous reasons—financial, technological, and political—only succeeded fifty-five years later when Palmer’s Permanent Bridge opened on January 1, 1805.

During this period, the best architectural and engineering minds of the city proposed numerous solutions. The first plan, submitted in 1767, was for a wooden bridge in a single arch some 400 feet in length and 47 feet above the water, but that proved unrealistic.

Two years later, on January 31, 1769, a Philadelphia architect named Robert Smith proposed building at least one wooden arched span, “. . . well covered to secure it from the Weather” (Griggs, 2009: 507). Though his proposal was ignored by the city assembly, it was the first known mention of covering a bridge in the colonies and foreshadowed Palmer’s Permanent Bridge. Another pioneering proposal appeared in 1774 when Thomas Gilpin of Philadelphia proposed building a suspension bridge with chains 400 feet long over the main channel approached by 300-foot-long abutments from each shore. Politician Thomas Paine, a man of many interests—both common and necessary in that day—proposed in 1786 both wooden and iron bridges, even building a 13-foot-long model of the iron bridge which he offered to Benjamin Franklin, who displayed it in his garden. The following year, Paine took that model to France, hoping for approval from the most highly respected bridge engineers in the world. Paine’s knowledge of iron bridges is all the more amazing considering that iron bridge technology had only just been introduced in England, first in a couple of obscure minor bridges and then prominently in Abraham Darby III’s amazing cast-iron bridge built over the River Severn in Coalbrookdale, England, between 1779 and 1781, only five years earlier. Because this was only possible due to the availability of iron from Darby’s nearby foundry, Paine’s idea for anything comparable in the United States was not yet feasible. Indeed, the city did not seriously consider Paine’s iron span because of concerns about its cost, the difficulty of procuring materials, and whether the abutments could withstand the weight.

In 1787, a plan with a drawing published in The Columbian Magazine (discussed earlier in this chapter) for a four-span wooden covered bridge with arches and a truss was likely a reworking of Smith’s 1767 plan. Who offered this proposal is unclear since Smith had died in 1777. Finally, two visionaries offered unrealistic plans for gigantic single spans, Frenchman Godofres Du Jareau in 1796 for a 300–400 foot wooden arch, and Charles Willson Peale’s own single arch, also discussed earlier. It is fair to say that rationality prevailed in most of these cases. Smith’s proposal for a wooden arched truss bridge, however, was the most realistic, but the main drawback was the impossibility of building the necessary piers in such deep water.

The term “permanent bridge,” in reference to the bridge Palmer eventually built on Market Street in Philadelphia, strikes some as odd, since clearly no bridge is ever permanent. The term derived from the desire to build a long-lasting solution to crossing the Schuylkill in contrast to earlier temporary solutions, and proposals, such as a military pontoon bridge, a floating log bridge, or a low stone bridge only passable in low water. Because this river, like most in the eastern United States, was prone to flooding and massive ice jams that swept all before them, even some of the more practical solutions that involved approaches restricting the river’s flow could not be considered. A complete history of the project appeared in 1806 that permits us not just to know the facts of Palmer’s bridge but, through the inclusion of numerous letters and other documents to hear the arguments for and against various aspects, especially the matter of covering the bridge. Originally a report written in 1806 titled “A Statistical Account of the Schuylkill Permanent Bridge, Communicated to the Philadelphia Society of Agriculture, 1806,” it was reprinted in 1815 in the Memoirs of the Philadelphia Society for Promoting Agriculture, Vol. 1.

Though the solution was not yet clear, Judge Richard Peters convinced the state legislature and governor to pass an “act for incorporating a Company for erecting a Permanent Bridge over the river Schuylkill, at or near the City of Philadelphia” on March 16, 1798, with Peters elected as President (Peters, 1815: 19–21). The Company offered 15,000 shares at $10 each for a total capitalization of $150,000, plus another 7,500 shares for unforeseen problems. Although still holding many unsold shares, the directors began searching for an affordable plan. Those proposed included one by William Weston, a British stone mason and engineer, who offered to build a series of stone arches. Another by Benjamin H. Latrobe, also of England, proposed a brickwork arch bridge. Still without a plan, the company hired a contractor to begin building the eastern abutment on October 18, 1800. Thanks to Weston’s advanced knowledge of hydraulics and coffer dams, the company decided to proceed with a pier in the shallower eastern channel, still hoping they might be able to bridge the western portion of the river (and the deeper channel) with a single span. Although challenging, the workers completed it during the fall of 1801. Judge Peters later wrote: “We know that no iron superstructure of such a span had been erected. We sent for Mr. Timothy Palmer, of Newbury Port, a celebrated practical wooden bridge architect. He viewed our site, and gave us an excellent plan of a wooden super-structure. But he pointedly reprobated the idea of even a wooden arch extending farther than between the position of our intended piers, to wit, 187 ft. He had at the Piscataway bridge, erected an arch of 244 feet; but he repeatedly declared, that wherever might be suggested by theorists, he would not advise, nor would he ever again attempt extending an arch, even to our distance, where such a heavy transportation was consistently proceeding” (1815: 71). There being no way to span the channel from the eastern pier to the western shore without an intervening pier, Weston and his masons proceeded to construct one in the deepest water—around 40 feet—beginning (oddly) on Christmas Day, 1802 and finishing it during the spring of 1803. Peters later wrote of this problem: “I have never in the course of my experience, or reading, heard of a pier founded in such a depth of water, on irregular rock, affording little or no support to the piles” (1815: 44).

Even though the piers were in place, Palmer, assisted by Mr Carr and other experienced workmen, only began building the superstructure in 1804, and although they expected the project to proceed quickly, in fact it took nearly a year to complete. But Palmer’s bridge, now benefitting from more than ten years of experience/ experiments in New England, was to be his magnum opus, a judgment accepted by observers at the time as well as the many travelers who later passed through the bridge and wrote glowing accounts of its great beauty.

The “Statistical Account” of 1806 summarizes the bridge’s dimensions: total bridge length was 550 feet, consisting of three spans, the outer two of which had clear spans of 150 feet each and the middle span an amazing 194 feet 10 inches. Adding the abutments and wing walls, the bridge covered 1,300 feet. The width was 42 feet, with an interior clearance of 13 feet for each of two lanes plus footways 5 feet wide on each side separated from the carriageway by “turned posts and chains.” The three trusses (two outer, one separating the roadways) each consisted of double arches rising from the masonry walls to the lower chords beneath the roadway plus slightly curved lower and upper chords rising 8 feet in a continuous arc (and avoiding the rise and fall of each span encountered in Palmer’s earlier bridges). The arches of the outer spans rose 10 feet while that of the middle span rose 12. The kingposts were not only radial but extended below the lower chords to the arches, as was also true of the braces. Each of the shorter spans had eight panels while the center span had ten. While the report says the carriage-way was 31 feet above the water, we are uncertain whether that was at the base or apex of the arches. In all, the bridge required 22,000 perches of stone—each equivalent to 24.75 cubic feet—and 1,500,000 board feet of timber. Its total cost came to nearly $300,000, a huge sum in those days.

Although the bridge opened on January 1, 1805, it remained unfinished in some ways and also uncovered. Judge Peters, though President, had been forced to accept the wishes of the Board in leaving the structure exposed to the weather. Some believed that covering it would cause water to be retained and prohibit drying, though Peters and Palmer believed that sealing the timbers with paint or some form of pitch would prohibit the timbers from becoming seasoned. Others feared that siding would play havoc with windstorms and cause the bridge to be blown from its foundations. Peters, apparently aware of Smith’s earlier advocacy of covering in 1769, had already sounded out Palmer on the matter of a roof and siding, for his letter to the Board of June 11, 1805, originally printed in the US Gazette in 1805 and included in the “Statistical Report” of 1806, its reprinting in 1815, and again in The American Farmer for November 16, 1821, quotes a letter he received from Timothy Palmer written on December 10, 1804. Although Palmer’s earlier bridges were not covered at the time of construction, Palmer indicated an understanding of its benefits. Palmer wrote: “. . . relative to the durability of timber bridges, without being covered sides and top, I answer, from the experience that I have had in New-England and Maryland—that they will not last for more than ten or twelve years, to be safe for heavy carriages to pass over.” After citing problems with the open bridges he had built earlier, he concluded: “And it is sincerely my opinion, that the Schuylkill bridge will last 30 and perhaps 40 years, if well covered” (1815: 48).

Philadelphia’s Market Street crossing of the Schuylkill challenged engineers for many years because they could not build stone piers. (Peters, 1815)

A clear rendering of both truss and deck structures of Palmer’s Permanent Bridge over the Schuylkill River on Philadelphia’s Market Street. (Weale, 1843; reproduced in Nelson, 1990: 14)

British-born painter William Russell Birch (1755–1834) arrived in Philadelphia in 1794, ten years before Palmer’s Permanent Bridge was completed. His painting of the uncovered bridge must have been done early in 1805 because by the end of the year Owen Biddle had roofed and sided the structure, creating America’s first documented “covered bridge.” (Encore Editions)

Birch’s etching, shown in the foreground along the shore and reproduced here, reveals the bridge after it was covered. (American Philosophical Society)

In Judge Peters’ letter to the board, he made the following argument. “From the time of the first idea of a wooden superstructure, I have never wavered in my opinion of the indispensable necessity of the cover.” Pointing out that covering the exposed timbers with paint, some other coating, or even with lead sheets leads to cracking, rotting, and feculation, he asserted that “Nothing has been proved so effectual, as covering the whole of a frame, constructed of large timber, with a roof; and, at the sides, excluding rain, without preventing an uninterrupted circulation of air” (1815: 46). Aware of the famous Schaaffhaűsen [also spelled Schauffhausen and Schaffhausen] bridge in Switzerland, he wrote: “It had been by its cover, effectually preserved from decay for thirty-eight years, and was perfectly sound, at the time the French [by Napoleon’s troops in 1799] destroyed it” (p. 47). He then quotes Palmer’s letter at length. Peters had earlier assumed the Board would agree to a cover and had already sketched plans for it, three of them submitted individually by Mr Dorsey, Mr Traquair, and Mr Owen Biddle.

At last the board relented and agreed to proceed, based on Peters’ estimate of $8,000. But first Peters also had to argue for the work being done immediately because some thought the wood might better age in the open for a year or so. Owen Biddle, one of the young nation’s premier builders and author of a handbook entitled The Young Carpenter’s Assistant; or A System of Architecture Adapted to the Style of Building in the United States, published in 1805, completed the work within the year. Wrote Peters: “It was executed with singular fidelity and credit, by Mr. Owen Biddle, an ingenious carpenter and architect of Philadelphia. . . .” (p. 27). Indeed, Biddle’s work gave the bridge an elegant appearance, with the lower arched portion not just painted to look like a stone arch with stone blocks above but with stone dust embedded into the paint. The upper portion consisted of vertical colonnades and twenty-two windows with shutters on each side.

The builders also carried out two other apparent innovations. For protection, they installed lightning rods along the roof, a technology whose invention is attributed to Benjamin Franklin in 1749 following his (in)famous experiment with a kite and a key. Later, to keep the decking boards from being worn, they installed planks lengthwise to carry the wheels of most carriages and wagons in addition to planks along the trusses to keep vehicles from damaging them. Peters also requested that William Rush, a prominent Philadelphia sculptor, be commissioned to create pediments at each end, the eastern one celebrating commerce and the western one agriculture. Finally, the company had “a pyramidical Pedestal, surmounted with four Dials, for the benefit of passengers,” which was an obelisk, erected at the eastern end celebrating those who erected the bridge, listing its vital statistics, and telling the story of the heroic efforts to erect the two piers (pp. 77–80).

Covered Bridges for a New Nation

Judge Richard Peters, President of the Board that built the Permanent Bridge, the first documented covered bridge in the United States, had not created the idea of preserving a wooden superstructure with roof and siding, but he appears to have been the first to persuade builders to actually cover a bridge. The Permanent Bridge is not just well documented but was seen and noted by virtually all of the many travelers who later published descriptions of their travels around Philadelphia. Although an iconic structure and the most perfect of Palmer’s many bridges, the Permanent Bridge had to be replaced in 1850, by which time bridge technology had advanced dramatically. By then, a bridge capable of carrying railroad trains as well as pedestrians and carriages was required, but building covered bridges such as this first had to become routine.

As noted earlier, Charles Willson Peale, writing in 1797, alleged that there were already covered bridges in the United States: “It has been advised to make roofs to cover Bridges, and some are so constructed in America.” But there is no known documentation of any actual bridges so covered. Peale’s statement implies that somewhere, perhaps in some smaller towns far from the cities, there were a few covered spans lurking. But it must be borne in mind that we are attempting to reconstruct a complete jigsaw puzzle with only a small percentage of the pieces. There is a likelihood that wooden trusses had developed as early as the 1760s. We know that the idea of covering bridges was known, both from Robert Smith’s statement in 1769 and the drawing in The Columbian Magazine from 1787. These ideas cannot have come from nowhere. It was also difficult for any one writer to know about distant areas, and in those days “distant” could have been a mere thirty miles depending on the existence of passable roads. There is ample documentation of the great bridges of the period, but it is unlikely that every bridge was noted.

After Palmer’s Permanent Bridge over the Schuylkill in Philadelphia was gutted by a fire in 1850, a replacement that added a rail line was built, but this was completely destroyed by fire in 1875. Shown is the third bridge on the site, a three-span massively arched Burr truss that lasted from 1875 to 1888 when it was replaced by an iron cantilever bridge. (Wikipedia Commons)

The populations of New England and Pennsylvania were very limited and infrastructure barely existed. Even in 1837, as described earlier by Englishman Robert Stevenson, America’s road system was deplorable, though New England’s was somewhat better. Nonetheless, before 1800, even in New England the road system was minimal. Neither federal nor state governments were building infrastructure at the time. Bridges, like roads, had to be built by private investors who contributed capital towards an enterprise that hopefully would pay a dividend through the tolls collected. Because there would be no incentive for a company to build a modest bridge on a back road—since users there could easily avoid tolls by crossing the stream in the usual way, by fording—the principal bridges being built were over major bodies of water and often of dramatic dimensions. It seems likely that most, if not all, of these larger bridges have been documented. Indeed, most were by Timothy Palmer himself, who affirms that none of his earlier bridges were covered (though some were retrofitted with covers after 1805). How would Peale know there were covered bridges elsewhere? Unless he had seen them with his own eyes, we must ask where were they? Possibly he had seen the drawing in The Columbian Magazine of January 1787. Perhaps he had heard of covered bridges in Europe and thought they were in the United States. However authoritative his statement may sound, there is no corroborating evidence. Thus, Palmer’s 1805 Permanent Bridge retains the title of “first covered bridge” until there is hard evidence showing otherwise.

This milestone, however, important as it is, privileges the least significant of Palmer’s innovations. Everything else about this bridge and the ones preceding it built by Palmer and the two Spoffords demonstrate the real progress made in American bridge design: the development of deep-water pier construction, the rapid evolution of timber bridge trusses, and the ability to construct massive spans of exceptional length and strength. After this, successive builders created ever more innovations in truss design, and America’s first professional engineers developed the science of stress analysis, making bridges ever more rational and efficient. Their story will be told in Chapter 2.

More Remarkable Bridges: Theodore Burr and Lewis Wernwag

After knowledge of Palmer’s Permanent Bridge spread, the idea of covering a wooden truss bridge to protect it from the weather was no longer considered odd or controversial. Covered bridges soon became the norm and continued to be so until the building of timber truss bridges was phased out during the late nineteenth and early twentieth centuries. The essence of covered bridges, then, is what the roofs and siding protect—trusses and other construction features. This vast subject will be treated systematically in Chapter 2.

Timothy Palmer, although having achieved near perfection in Philadelphia, built at least one more bridge before his death in 1821, the three-span 490-foot bridge over the Delaware between Easton, Pennsylvania, and Phillipsburg, New Jersey. Theodore Cooper visited this bridge in the 1880s and reported: “This bridge, after eighty-four years’ service, is still in use and about five-sixths of the original timber is in good condition. It has always been covered in from the weather” (1889: 8). His Plate V includes a drawing of the truss, demonstrating that it was a virtual copy of the Permanent Bridge. Photos show that he even copied the painted-on stone arch bridge effect for the lower portion along with a similar series of windows above (Allen, 1959: 52). This was possibly America’s second documented covered bridge.

Overlapping Palmer’s time, however, was the next up-and-coming bridge builder, Theodore Burr (1771–1822), whose short life included some of the most ambitious and daring bridge projects ever attempted in the United States. Though he was born in Torringford, Connecticut, Burr’s major bridges spanned rivers in New York, Pennsylvania, and Maryland. The son of a millwright, he moved to Oxford, New York, in 1792 to continue his father’s craft. Thus, his earliest work included a local grist mill, a dam, and an open bridge over the Chenango River in Oxford, a small village located midway between Binghamton and Utica. Successful as a builder, between 1809 and 1811 he built for himself a large Federal-style house in Oxford which, years later and with two added wings, became the Oxford Memorial Library and is now the home of the Theodore Burr Covered Bridge Archive. Burr’s many bridge building activities, however, necessarily kept him from enjoying his grand home.

Palmer’s last bridge, connecting Easton, Pennsylvania, to Phillipsburg, New Jersey, across the Delaware River was 490 feet long in three spans, nearly identical to his Permanent Bridge. Built before his death in 1821 and covered from the beginning, the bridge was finally torn down early in the twentieth century. (NSPCB Archives, R. S. Allen Collection)

Fortunately, a number of original letters written in Burr’s hand survive, giving us a first-hand impression of the man. Hubertis M. Cummings’ authoritative article published in 1956 in Pennsylvania History offers the best summary of his work. Since Burr moved with his young bride, Asenath Cook, to Oxford just as Palmer was beginning to build innovative bridges in Massachusetts, it is doubtful that Burr ever saw them. With skills in mill construction but little bridge experience, Burr nonetheless boldly entered the bridge building business. Between his 1800 debut in building the bridge in Oxford and 1808, he constructed at least seven more bridges, none known to have been covered at the time of construction. The first of these was a 400-foot “drawbridge” over Catskill Creek at Catskill in 1802 followed by a 330-foot bridge at Canajoharie over the Mohawk River. Of these we know little, but clearly Burr’s early bridges exhibited an experimental spirit. Where Palmer created and perfected a specific pattern combining truss and arch, Burr tried out completely original structures in his Mohawk and Trenton bridges as well as used a more conventional truss-arch pattern in other bridges, the latter becoming the foundation of what we now know as the “Burr truss.”

Because of its longevity, we know much about the Lansingburgh-Waterford Union Bridge in New York State, built in 1804. With a length of 800 feet, it was the first bridge across the Hudson River. Consisting of four two-lane spans, each a different length ranging between 154 and 180 feet, its level roadway passed through triple trusses of X panels and massive arches, each of the latter having eight layers of wood bolted together. Had Burr covered it initially, he might have beaten Palmer for the distinction of “first covered bridge,” but his massive arches were left exposed until 1814. Because the bridge lasted until it burned in 1909, there are numerous photos. Compared to others he built, this was fairly “conventional.”

Far more experimental was Burr’s next project, the five-span bridge over the Delaware at Trenton, New Jersey, with two spans measuring 203 feet each, one at 198 feet, one at 186 feet, and the last at 161 feet, these said to be “clear” spans. Thus, the bridge’s total length was well over 1,000 feet. Cooper, who also visited this long-lasting bridge, originally built between 1804 and 1806, described its construction: “Each span had five arched ribs, formed of white pine plank, from thirty-five to fifty feet in length and 4 inches thick, repeated one over the other, breaking joints, until they formed a depth of 32 inches. . . . The roadway was suspended from the arch ribs by vertical chains. The arch was counter-braced by diagonal braces, formed of two sticks 6 x 10 inches spiked to the lower chord and secured to the arch above by iron straps” (1889: 8–9).

Although the bridge lasted until 1875 when it was replaced by one made of iron, it had undergone various renovations in 1832, 1848 (to carry trains), and 1869. Cooper includes a clear drawing of the structure, including the flared ribs out 50 feet from the abutments and piers designed to provide bracing against the wind. Never covered in the conventional sense, Burr’s successful experiment had a partial roof over the top that followed the contours of the arches.

Bold to the point of brazen, Theodore Burr’s 1,000-foot crossing of the Delaware between Trenton, New Jersey, and Morrisville, Pennsylvania, was unprecedented in design and only partially covered. (NSPCB Archives, R. S. Allen Collection)

Burr and Palmer were contemporaries, but Burr succeeded in building bridges with level roadways when Palmer’s were arched. The Lansingburgh-Waterford Union Bridge over the Hudson used Burr’s usual design, having a panel truss with both braces and counterbraces, along with laminated arches. (NSPCB Archives, R. S. Allen Collection)

Carrying both carriages and light rail, Burr’s Lansingburgh-Waterford Union Bridge crossed the Hudson River in four spans of varying length, totaling 800 feet. Built open in 1804, it was not covered until 1814 but lasted until 1909 when it burned. (NSPCB Archives, R. S. Allen Collection)

Burr’s Delaware River crossing, connecting Morrisville, Pennsylvania, to Trenton, New Jersey, was one of the most noted bridges of its time, 1806–75. (NSPCB Archives, R. S. Allen Collection)

Theodore Cooper provided detailed drawings of Burr’s experimental design at Trenton, New Jersey. The gigantic arches supported a combination of vertical iron chains and diagonal wooden beams to secure the deck, with only a partial roof over the arches. (Cooper, 1889; reproduced in Nelson, 1990: 17)

Originally built uncovered, then covered, the wooden suspension design of the Mohawk bridge required additional piers by 1828. This photo, taken during its dismantling in 1873, allows us to see its deteriorated trusses. (NSPCB Archives, R. S. Allen Collection)

Far less successful was Burr’s Delaware River bridge between Schenectady and Scotia, New York, built in 1808 in four spans following a failed attempt to cross the river in two spans. (NSPCB Archives, R. S. Allen Collection)

Burr’s next project, aptly described by Cooper as “a curiosity,” demonstrates both Burr’s originality and his daredevil nature. According to Cooper, Burr’s first attempt to bridge the Mohawk River in 1808 between Schenectady and Scotia, New York, resulted in disaster when one of the two spans, each apparently 450 feet long, either collapsed or was swept away. His second attempt, according to the contract quoted by Cooper, placed the bridge at the same site but with additional piers. A double-lane bridge tightly covered under roof and batten siding at some point, it was an experimental wooden suspension bridge. Says Cooper: “The curved ribs are formed of eight 4 x 11-inch planks spiked or bolted together” (1889: 9). Cooper’s drawing, copied from that attached to the contract seen by him, shows an undulating wooden “chord” rising like an arch above the piers and sweeping to the deck level between, in the manner of a suspension bridge. While chain suspension bridges were already well established, it is doubtful anyone had tried to use laminated wooden “cables” in extreme tension. Additional bracing, both vertical and diagonal (the latter from the piers), could not maintain stability. According to an old photo, engineers had tried to reinforce the bridge with additional bracing (Mohr, 1957b: 5). By 1828, six years after Burr’s death, the spans were sagging dreadfully and had to be shored up with new piers between the original ones. Though it looked like a wet blanket stretched over supports and must have given passengers seasickness as they rose and fell over each span, this bizarre-looking crossing lasted until 1873. Though it served sixty-five years, it was clearly a design failure from the start.

Perhaps recognizing that the Mohawk River plan had flaws, his next project was a three-span bridge over the Schoharie River at Esperance, first contracted in 1809 but not completed until January 12, 1812. An interior photo of this last Burr bridge to survive (until 1930) shows a double-lane bridge with three trusses. The downstream photo clearly shows that Burr had constructed three spans with gently curved arches below the roadway, a feature standard in Palmer’s bridges. The truss, however, bears no resemblance to Burr’s later design, having as it does double panels that resemble half-sized kingpost trusses. Such trusses were probably intended to strengthen the arches, which likely bore most of the weight.

Following his work in New York State, Burr was lured to Pennsylvania eventually to build four superlative bridges over the mighty Susquehanna and a fifth over the same river in Maryland. While all but one were conventional covered bridges, using some form of what had come to be known as the “Burr truss,” none was of modest proportions, not surprising considering that the Susquehanna is, as some joke, “a mile wide and an inch deep.” The various bridge companies began applying for state approval in 1807. As each was approved, contracts were drawn up with builder Burr, all of which are discussed in Cummings’ 1956 article, which also includes a photo of a small wooden bridge model probably made by Burr himself and now preserved by the Pennsylvania Historical and Museum Commission. Between late February 1812 and 1815, Burr completed the five bridges in Pennsylvania, and before 1818 the sixth one in Maryland. From north to south, each was remarkable.

This photo, taken shortly before the Mohawk bridge between Schenectady and Scotia was removed in 1873, shows how badly it sagged in spite of the extra piers, demonstrating that wood does not work well as a suspension member placing extreme tension on a material that works better in compression. (Ronald G. Knapp Collection)

The Mohawk crossing was a failure in spite of added piers and an immense number of extra braces, giving the trusses the look of some of Europe’s heavily timbered covered bridges. (NSPCB Archives, R. S. Allen Collection)

Built in 1812, Theodore Burr’s bridge over Schoharie Creek at Esperance, New York, used arches below the deck in the manner of Timothy Palmer. (NSPCB Archives, R. S. Allen Collection)

This rare photo allows us to see the under structure, with the arches below the deck and a heavy deck system. (NSPCB Archives, R. S. Allen Collection)

Burr’s bridge over Schoharie Creek at Esperance, New York, with only three spans and a single lane was among his simplest. It lasted until 1930. (NSPCB Archives, R. S. Allen Collection)

1. Perhaps the most modest of Burr’s bridges, and the least known, is the multi-span bridge over the North Branch of the Susquehanna between Nescopeck Falls and Berwick, southwest of Wilkes-Barre.

2. The bridge between Northumberland and Sunbury also crossed the North Branch near its confluence with the West Branch and was separated into two portions of three spans each by an island. According to the contract, there were two carriageways, each 11 feet 6 inches wide with a 4-foot-wide footway between. In the contract, the bridge had to be roofed with shingles and sided.

3. The bridge at Harrisburg, like that at Northumberland, was divided by an island and in total consisted of twelve 210-foot spans in two segments of six each. Begun in 1812 and completed in 1817, the eastern portion survived until 1902 and the western until 1903. It was the western portion, however, which caught everyone’s attention because the roadway gently rose and fell with the gigantic arches that were embedded into the abutments and piers far below the deck. Because of this feature, the bridge was widely known as the Camelback Bridge.

4. Although Burr is credited with designing the bridge between Columbia and Wrightsville, the contractors were Jonathan Walcott, Henry Slaymaker, and Samuel Slaymaker. It is hard to imagine how much stone and timber went into constructing a bridge consisting of twenty-six spans of 200 feet each, for a total of 5,690 feet, more than a mile in length and the longest covered bridge ever built. At that time, Pennsylvania was still covered with primeval forest and timber was easily and cheaply available. By the end of the century, however, with the expansion of the tanbark industry and the proliferation of tanneries dependent on a steady supply of hemlock bark and fuel, the building of tens of thousands of wooden houses in towns throughout the east, and countless mills and covered bridges built, including several replacements for Burr’s original crossing, Pennsylvania’s once magnificent hills and mountains had become denuded.

5. If Columbia-Wrightsville was grandiose in proportions, the McCall’s Ferry Bridge, farther south where the river is squeezed through its narrowest point, was stunning for both its span length and the radically innovative manner of its construction. The river, racing between hills that brought about weather more turbulent than normal, had a deep narrow channel along with a shallow area in York County. At low water, that portion was exposed, and building a pier at this point was simple. The remaining distance to the Lancaster County shore, however, was 360 feet, and no one had built a successful span of this magnitude before. Theodore Burr, nonetheless contracted to do just that. But with the river bottom 100 feet below the bridge deck, there was no way to erect scaffolding. Burr decided to build his scaffolding on floats instead, and the arch was built standing vertically along the river shore on the floats, whose ropes had to be adjusted continuously to compensate for the changing water levels. The arch was ready by December 7, 1814, but the river gave them problems by freezing and creating masses of ice, threatening to destroy the greatest wooden arch ever constructed. Always a quick thinker, Burr directed the arch to be cut into two halves and one of them eventually placed on rollers and moved out onto the ice which workers had smoothed flat. Over a significant amount of time and with the efforts of hundreds of local residents called out to help, they managed to turn the arch halves into line and hoist them onto the pier and abutment, then lock them back together. Considering the weight of the arch and the extreme weather conditions, this was a superhuman feat. During January and February, his crew was able to complete what Cummings called “a feat of engineering hitherto unparalleled in America,” building two arched truss spans, one 376 feet long with a clear span of 360 feet 4 inches, the other having a span of 247 feet, all the arches having been raised on floating falsework (Cummings, 1956: 482). With a width of 32 feet, the bridge provided ample passage for the many farm products of the area that needed to go to markets in Philadelphia and other points east, since this was the only bridge from Columbia-Wrightsville near Harrisburg to south of the Maryland border.

Burr’s Susquehanna River bridge at Harrisburg consisted of twelve spans, each 210 feet long. It was divided into two bridges by an island, each segment comprising six spans. (Rathmell, 1963: 4)

The western portion was more noted than the eastern portion because of its distinctive shape, giving rise to its nickname, the “Camelback Bridge.” (NSPCB Archives, R. S. Allen Collection)

Each span of Burr’s “Camelback Bridge” at Harrisburg, Pennsylvania, was 210 feet long, equal to the “longest single-span covered bridge” at Blenheim, New York, that stood until 2011. Typical of Burr’s bridges, the truss portions had both braces and counterbraces, but the massive three-piece arches caused the rise and fall in the deck that gave rise to the “camelback” moniker. (Dauphin County Historical Society, Pennsylvania)

The third Columbia-Wrightsville bridge over the Susquehanna River in Pennsylvania was a Howe truss rail bridge in twenty-seven spans built in 1868 and destroyed by a tornado in 1896. The first was designed by Theodore Burr, built by others in 1812, and then destroyed by ice in 1832. The second was finished in 1834 and burned by Union troops during the Civil War. (NSPCB Archives, R. S. Allen Collection)

The “camelback” segment in the west totaled 1,260 feet in six spans, somewhat shorter than today’s “World’s Longest Covered Bridge” at Hartland, New Brunswick. (Terry E. Miller Collection)

Shortly after completing the bridge, Burr wrote a letter on February 26, 1815, to his friend, fellow bridge builder Reuben Field of Waterford, New York, detailing how the bridge was built. This is probably the most detailed historical description of bridge building known and helps us appreciate just how overwhelming this task was (Burr, 1815). In the letter, Burr exclaims: “This arch is, without doubt, the greatest in the world. . . . The altitude or rise of the arch is thirty-one feet. The arch is double and the two segments are combined by kingposts seven feet in length between the shoulders, and are united to the arch by lock-work. Between the kingposts are truss braces and counteracting braces. The arch stands firm and remarkably easy, without the least struggling in any part of the work.” As detailed as this account is, it leaves many questions unanswered. If the bridge is 32 feet wide, as Burr writes, then it suggests two lanes. Burr writes of the raising of only one arch. Before proposing a solution, readers need to know that Burr’s triumph was short-lived. On March 3, 1818, while Burr was still working on the Susquehanna bridge at Rock Run, Maryland, the natural forces of water and ice ripped the McCall’s Ferry Bridge from its foundations and smashed it against the rocks along the river. Even to this day, there is no crossing at McCall’s Ferry. But there is a clue. Burr’s otherwise little known and short-lived bridge over the Mohawk at Canajoharie, New York, built in 1806, was described as a single arch of 330 feet. In June, 1808, Anne M. H. Hyde de Neuville painted “Incomplete Bridge, Palatine” of the remains of one end of the bridge. It shows two trusses, each with the arch as the lower chord and reinforced with a framework of posts and cross bracing. Assuming that the McCall’s Ferry Bridge was similar, we can surmise that Burr had the entire framework built on the floating falsework, cut the bracing between the trusses, and moved each separately over the ice onto the stonework. Burr was unchallenged on his genius and daring.

6. Burr’s final bridge over the Susquehanna was between Rock Run and Port Deposit, villages halfway between Conowingo and today’s I95 in Maryland and whose former tollhouse is in what is now Susquehanna State Park. The bridge, consisting of eighteen spans, each 200 feet, with eight from the western shore to the first island, two to the second island, and eight from that to the eastern shore for a total length of 4,170 feet, was completed in 1818. Beginning in 1823, it suffered a series of calamities. First, on January 1, the eastern half was set on fire from a spark generated when a sleigh rail scraped a nail head. Lewis Wernwag, Burr’s greatest contemporary (though Burr had already died the year before), rebuilt the damaged spans. Another fire in 1828, now on the western side, required the rebuilding of six spans, again by Wernwag, which he completed by September, 1831. The bridge’s final disabling came on October 27, 1854, when a herd of cattle coming from Port Deposit collapsed or damaged four spans. At this point, officials decided to abandon the bridge. On February 11, 1857, an ice floe administered the coup de grace, bringing down much of what remained.

The last four years of Burr’s life were ones of misery and stress. There are unconfirmed reports that he may have built some modest bridges and might have been in the middle of a project in Pennsylvania when he died. Though he was a bold, innovative, and ambitious bridge builder, he was far less skilled in managing money, for coordinating the construction of and payments for multiple bridges simultaneously necessitated a small army of accountants. Just as ice so often bunched up and destroyed covered bridges, mounting debts and competing demands for cash flow brought Burr’s otherwise glorious life to an early end. All that is known is that Burr died in Middletown, Pennsylvania, in November 1822. Nothing is known of the cause of death or the whereabouts of his burial. Of all of America’s many bridge builders, Theodore Burr stood out as the unrivaled leader, but, like his mighty McCall’s Ferry Bridge, his fame was short-lived and he left the scene suddenly. Most builders after Burr were less visionary and more reasonable, though one more daring bridge builder requires inclusion.

Built in 1806 and already having collapsed by the time this painting was made in 1808, Burr’s bridge over the Mohawk River at Canajoharie, New York, at 330 feet was as daring as it was unsuccessful. “Incomplete Bridge, Palatine, New York” by Baroness Anne-Marguerite-Henriette Hyde de Neuville (c. 1761– 1849) (watercolor and graphite on paper), 1808. (Acc. #1953.211, Collection of The New-York Historical Society)

He was Lewis Wernwag (1769–1843), born in Riedlingen, Wurttemberg (Germany). Coming from a millwright tradition, he immigrated to Philadelphia in 1786, likely to escape military conscription and the endless conflicts in central Europe. There he began erecting mills and making mill wheels. Though without training in bridge design, he built an open draw-span bridge over Neshaminy Creek around 1810 on the Frankford-Bristol Turnpike just northeast of Philadelphia, the design of which is thought to be shown in an engraving from around 1815 by Enoch G. Gridley. This was apparently his only preparation for designing and constructing one of the most daring bridges actually built in the United States. Because the records of the construction of this grand bridge over the Schuylkill, officially the Lancaster-Schuylkill Bridge but also known as the Upper Ferry Bridge or the Fairmount Bridge, are extant, engineering historian Lee H. Nelson could write a detailed history which recognizes the bridge by the name Wernwag dubbed it: The Colossus of 1812: An American Engineering Superlative (1990). Thirty-one years earlier, Richard Sanders Allen had featured the bridge in his Covered Bridges of the Middle Atlantic States (1959) and provided a color reproduction of the painting by Thomas Birch as the frontispiece.

Even though Palmer’s Permanent Bridge crossed the river nearby, a group of businessmen proposed a second crossing on January 30, 1811 and called for proposals. At first, only two proposals came in, an implausible one by the visionary Thomas Pope, and two designs—now lost—by architect Robert Mills, one uncovered, one covered. Only later did Wernwag step forward with a design for a triple-arched structure reinforced with a truss with an unprecedented clear span of 340 feet with two lanes. On December 5, 1811, the company contracted with Wernwag based on the believability of his presentation and the use of a well-constructed scale model to build the bridge. Wernwag demonstrated great wisdom in anticipating a number of problems and designing solutions, especially the problem of rot developing between members: “This Bridge has a superiority of any other, having near 100 feet span [sic], more than any in Europe or America. The dry rot is entirely prevented by the timber being sawed through the heart, for the discovery of any defect & kept apart by iron links & screw bolts, without mortice or tennon, except the king posts & truss ties. No part of the timber comes in contact with each other, & can be screwed tight at any time when the timber shrinks. Any piece of the timber can be taken out & replaced if required without injury to the Superstructure” (quoted in Nelson, 1990: 21).

Wernwag’s design is known to such an extent that it could be reproduced today. The main structural element was a series of massive wooden arches, each composed of six members joined in pairs to create three arches. Because of his concern for dry rot, Wernwag designed an ingenious iron bracket, two per panel, that separated the members and yet preserved their working in union. The arches together acted as the lower chord. Above it were panels having double 6 x 12 inch kingposts and each made rigid with braces and counterbraces, apparently of equal size. There were systems of iron bars, rods, and clamps, including ones that anchored the entire bridge diagonally back into the abutment walls, throughout the structure. Lateral bracing was anchored to what he called iron “boxes” placed on the tops of the kingposts. The upper chord did not run parallel to the arches, having a flatter curve, giving the bridge a flared shape, with the middle narrower than the ends. Overall, the design was as sophisticated as any ever proposed in the United States or Europe, and the ease with which Wernwag completed the construction was also amazing.

Lewis Wernwag’s Colossus, opened on January 7, 1813, was 340 feet long in a single span, the longest such bridge at that time. While it could have served many more years, arsonists destroyed the structure in just twenty minutes in 1843. (Yale University Art Gallery)

“A View of Fairmount and the Water-Works, c. 1837” (watercolor, pencil and gouache) was painted by John Rubens Smith from the perspective of a hotel verandah looking towards Wernwag’s monumental Colossus. It clearly shows the bridge within the context of human life at the time in a city that was still quite compact. (Bridgeman Art Library)

Wernwag designed a bridge primarily supported by three compound arches that doubled as lower chords with an upper chord that, while curved, was non-parallel. These were made rigid with posts and braces. (US Patent Office)

William Strickland’s painting, “A View of a Bridge over the Schuylkill River” (oil on canvas), actually shows America’s two most important bridges of the time, Palmer’s Permanent Bridge in the foreground and Wernwag’s Colossus upriver in the distance. Although part of Philadelphia’s city streets, the surroundings indicate how much open countryside remained. (Bridgeman Art Library)

The bridge, which was not covered at first, was officially opened on January 7, 1813. As related years later by John Wernwag, Lewis Wernwag’s son, there was great apprehension that when the scaffolding was removed, the bridge would fall. Wernwag famously brought the nervous company managers to the bridge before the ceremony, who asked, “Well, Lewis, do you think our bridge will stand the test today?” Wernwag answered, “Yes, gentlemen, it will” (quoted in Nelson, 1990: 24–5). He then showed them that he had removed the blocks between the bridge and scaffolding the day before, and the bridge was already supporting itself. It was not until March 13 that the company agreed to “roof and finish” the bridge with a shingled roof and ten windows with shutters at a cost of about $90,000.

Although Wernwag’s record for building the longest single-span wooden bridge fell to Burr’s short-lived McCall’s Ferry Bridge in 1814, nature was kinder to the “Colossus of Fairmount” than to the McCall’s Ferry structure, destroyed by flood waters only three years later. A hurricane that struck Philadelphia on September 3, 1821 tore off the roof and siding of the Colossus. But just four years before Wernwag’s passing, in 1843, arsonists accomplished what nature had failed to do: by setting fire to the bridge and causing it to fall into the river within only twenty minutes. The crossing remained without a bridge for four years, until Charles Ellett Jr built an innovative suspension bridge using woven wire rope.

Having begun his bridge building career with his capstone achievement, Wernwag could devote himself to less ambitious projects. As related by Richard Sanders Allen: “From then on, Wernwag practically had to fight off agents from bridge companies. Usually they would offer a big block of stock in their infant organizations, but sometimes there was cash on the barrelhead. The now famous inventor chose only the best offers, and the next few years found him building bridges across the Delaware at New Hope, over the Schuylkill at Reading, and spanning the Susquehanna at Wilkes-Barre. Out in Pittsburgh in 1816, he erected that growing city’s first bridges across the Allegheny and the Monongahela” (1959: 16).

Of these, one in particular stands out, the bridge over the Delaware River at New Hope, Pennsylvania, which was built between 1813 and 1814. The six spans of 175 feet each, for a total of 1,050 feet, were constructed using an innovative truss designed by Wernwag and apparently not used again. As was typical in that day, the bridge was 32 feet wide, with two carriageways and flanking pedestrian walkways. According to an engraving that showed this design, along with that of the Colossus and a swing bridge, the structure consisted of a laminated or multi-sectioned arch resting on the lower chords at each end, and a panel truss of wooden kingposts and iron rods apparently in tension, because they are placed diagonally from the center towards the ends—the reverse of the wooden braces found in more usual trusses. There appear to be numerous iron separators and clamps similar to those he proposed for and used on the Colossus.

After this, Wernwag became involved in a number of industrial projects, but the business practices of the day made such investing risky, and Wernwag’s involvement in what came to be the Phoenix Works, a large mill making iron implements, came to naught, when, as a result of the war of 1812, the firm went bankrupt. He also invested in a lumber mill at Conowingo, Maryland, which manufactured precut timbers for trestle bridges in Tidewater Virginia, and there he built a ten-span covered bridge over the Susquehanna to facilitate customers crossing to his mill. When Burr’s Port Deposit Bridge was heavily damaged by fire in 1823 and 1828, Wernwag was called in each time to rebuild the lost spans. Finally, in 1824, he moved to Harpers Ferry, Virginia (now West Virginia), where he purchased an island in the Shenandoah near its junction with the Potomac. Emory Kemp sums up his career: “In 1824 he purchased the Isle of Virginius at Harpers Ferry, Virginia . . . and there established a manufacturing center. This move to Virginia brought him into contact with the Baltimore and Ohio Railroad (or B&O), for which he built bridges, the most notable being a Y-shaped bridge over the Potomac at Harpers Ferry [1842]. Ironically, one of Wernwag’s smallest structures was to become famous as a result of John Brown’s raid in 1859—the engine house at Harpers Ferry that sheltered Brown and his men during the abortive raid” (2005: 11).

As with Burr and Palmer, none of Wernwag’s bridges have survived, though the engine house remains as part of the Harpers Ferry National Historical Park. Where Burr’s truss design became a dominant one, those used by Palmer and Wernwag are only echoed faintly in a few bridges surviving today. Many continue to call Burr trusses with flared (radial or fanlike) posts a Wernwag truss, but this pattern is not a patented feature. Many builders in addition to Lewis Wernwag used such a variation.

Following Independence in 1776 and the end of the Revolutionary War with the Treaty of Paris in 1783, the people of the young United States were energized to develop their vast land at almost any cost. With a relatively small population and little educational infrastructure, the citizenry had risen to the needs and martialed a degree of creativity and boldness unimaginable in old Europe. What was later called “American optimism” led self-taught craftsmen with little or no training in bridge design not just to construct grandiose bridges in astoundingly difficult circumstances but to also imagine solutions that were unlikely to have been conceived in Europe at that time. And they accomplished this at a time before the advanced technologies of material, design, and construction equipment had sufficiently developed. It is difficult for us, used to seeing powerful cranes capable of lifting virtually anything, including whole bridges, to imagine how mere mortals using little more than horses, ropes, pulleys, and simple derricks could span some of America’s widest and most treacherous rivers. We try to understand the bravery of men who could create coffer dams in deep water with little technology, and then descend into them, somehow building piers of multi-ton blocks of stone, knowing that if the dam gave way, they were instantly gone.

Because it straddled the boundary between the Union and the Confederacy, Confederate Brigadier General Joseph Johnson burned the Harpers Ferry bridge on June 14, 1861. Its temporary replacements, all built by the B&O Railroad, were destroyed three more times by war and five times by flooding during the war period alone. (Harper’s Weekly, 1861)

Designed by Lewis Wernwag and built by Benjamin H. Latrobe II (1806–78) for the B&O Railroad in 1837, the great bridge over the Potomac near its confluence with the Shenandoah River at Harpers Ferry, Virginia, added a “Y” branch in 1839 to eliminate a curve. The bridge became famous when John Brown crossed the bridge in 1859 to raid the armory. (NSPCB Archives, R. S. Allen Collection)

Lancaster County in Pennsylvania is home to both a large Amish population and numerous covered bridges. Erb’s Bridge over Hammer Creek, built in 1887, is typical, having a Burr truss and stout stone parapets securing the approach. (A. Chester Ong, 2011)

The Diffusion of Covered Bridges Throughout North America

By the 1820s, knowledge of American timber bridge truss technology was not just spreading to a rapidly growing corps of young builders but over an increasingly wide geographic area. Palmer and Burr had evolved designs based on the fundamental principles of triangle and arch framed in wood, but Wernwag experimented both with design and materials, increasingly using elaborate iron elements such as spacers that separated pieces of his arches to prevent dry rot. Timber truss bridges thus evolved rapidly in the hands of the first generation of builders from 1792 to the 1820s. The idea of covering them, though discussed as early as 1769, became a documented reality only in 1805 with Palmer’s celebrated Permanent Bridge. After that, “covered timber truss bridges” became the norm. The earliest bridges had been built where the population was concentrated, from Massachusetts south to Maryland and New Jersey and in eastern New York and Pennsylvania. Movement to the west and much of the south was obstructed by the Appalachian Mountain range. In mountainous or hilly regions, towns were founded along rivers because these provided transportation, power, and water supplies, though sometimes also ice jams and floods. The same held true as explorers and pioneer families explored the territories to the west and south, establishing towns in areas formerly occupied by the native peoples who were mostly forced off their lands, either into reservations or migration to the barren lands farther west.

Westward expansion naturally pushed past Pittsburgh into Ohio, then Indiana and Kentucky, and on to Indiana, Illinois, and Missouri. Towards the south, people migrated into the Appalachians, including what became West Virginia, western Virginia, the Carolinas, and then Georgia, Alabama, and Mississippi. As they settled in these newly populated areas, they encountered the same problems earlier generations had struggled with in New England and the Middle Atlantic states: vast roadless forests, unbridged rivers, and mountain terrain. As was true earlier in the east, there were no “bridge engineers” per se among them, that science not yet having developed in the young United States, but many were experienced in building homes, mills, and churches, and they too—though perhaps having learned something from the examples set by Palmer, Burr, and Wernwag—set about teaching themselves to build bridges. The covered bridge became the norm, though generally on a more modest scale.

Throughout the rest of the nineteenth and well into the twentieth century, timber truss covered bridges proliferated throughout the eastern half and to a lesser degree in the western half of the contiguous forty-eight states. Covered bridges were also constructed in Hawaii in the late nineteenth century and in Alaska during the first decades of the twentieth. Over time, they became merely “normal,” as newsworthy as concrete and steel highway deck bridges are today. Until the advent of iron bridge technology, especially after the Civil War, there were few alternatives: open wooden bridges, pony truss bridges, stone arch bridges, and simple stone culverts.

Adjacent to Greisemer’s Mill in Berks County, Pennsylvania, the covered bridge built in 1868 over Manatawny Creek is 140 feet long. (A. Chester Ong, 2010)

By 1902, Pittsburgh had at least a dozen bridges over its two rivers, only one being covered. When the covered Union Bridge was built in 1875, Pittsburgh already had its first iron suspension bridge, which was built in 1859 by John Roebling, the German-born engineer who later built the Brooklyn Bridge. The covered bridge, too close to the water, was a nuisance well before it was damaged in the flood of 1907 and replaced. (Library of Congress)

Spanning the Allegheny River at Pittsburgh’s “Point,” where it joined the Monongahela River to form the Ohio River, the Union Bridge was the first at this location, having been built in 1875 to carry pedestrians, carriages, and the trolley. (Thomas and Katherine Detre Library and Archives, Senator John Heinz History Center)

Pittsburgh’s Union Bridge consisted of five spans supported by especially powerful Howe trusses with triple rods reinforced with massive laminated arches. Such a structure was needed to support such a wide bridge with long spans and heavy traffic. (Carnegie Museum of Art, Pittsburgh; Gift of the Carnegie Library of Pittsburgh)

The first, and perhaps the only covered bridge over the Ohio River, connected Wheeling’s island over the west channel to Bridgeport, Ohio, on the National Road. Designed by Lewis Wernwag, the bridge, consisting of three double-lane spans using doubled Burr trusses, was constructed from 1833 to 1836 (some say 1837) by Noah Zane. It was not replaced until 1893. (NSPCB Archives, R. S. Allen Collection)

We can never know just how many covered bridges were built in the United States (and later in Canada as well), but two individuals, Bill Caswell and Trish Kane, are seeking to do just that. Still a “work in progress,” their website, www.lostbridges.org, seeks to list every covered bridge that exists now or existed in the past in the United States and Canada. As of April, 2012, they had listed 12,895, but certainly this inventory is incomplete. Some states, such as Ohio, have been thoroughly researched while others have not, which likely skews the data. Nonetheless, we can gain some indication of relative numbers of bridges and their ages from the website. The data show a clear pattern of covered bridge building concentrations and document a chronological expansion of the phenomenon. They also provide some indication of how few remain today.

The old patterns continued. Private companies built turnpike (toll) roads connecting towns and cities as well as into the wilderness, but increasingly the United States Government became involved. In 1811, Congress authorized the building of the “National Road” from Cumberland, Maryland, across West Virginia, Pennsylvania, Ohio, Indiana, and Illinois, terminating at St. Louis, Missouri. By 1818, the road had reached Wheeling, but in 1837, resulting from a “panic,” funding ceased, leaving the road completed only to Vandalia, Illinois. In addition to using Scottish engineer John Loudon McAdam’s technique of constructing roads using pebbles instead of stone blocks or bricks pressed into the soil, the so-called “macadam roads,” designers began to construct handsome stone arch bridges. These included the seemingly mysterious “S Bridges,” mostly in Ohio, so-called because of curves at each end necessary to approach a bridge built perpendicular to the creek. The builders of the National Road, as well as builders of other turnpikes connecting to it, also built covered bridges, with most of them being double lane. Urban bridges also usually had at least one pedestrian sidewalk as part of the bridge. Perhaps the longest crossed part of the Ohio River from Wheeling Island to Bridgeport, Ohio, on the National Road and was a three-span Burr truss structure designed by Lewis Wernwag in 1836. Although nearly burning down in 1883, the bridge survived until 1893 when it was replaced with an iron bridge. Other covered bridges on the National Road and associated turnpikes were among the earliest bridges built in Ohio and Indiana.

Though the National Road was the nation’s most important traffic artery, even in 1912 when this vintage car passed through a typical double-lane bridge near Effingham, Illinois, the surface was dirt and subject to deep ruts and other obstacles. (Photography Collection, Miriam and Ira D. Wallach Division of Arts, Prints, and Photographs, The New York Public Library, Astor, Lenox and Tilden Foundation)

Although most sources say Virginia’s Humpback Bridge was constructed in 1835 by Messrs Venable and Kincaid for the Kanawha Turnpike, later research shows that it was constructed in 1857 by an unknown builder. This narrow soil-surfaced road ran 208 miles from the James River to the Kanawha River through central Virginia. (Terry E. Miller, 2012)

Chillicothe, Ohio’s Bridge Street Bridge over the Scioto River, was built in 1817 to carry the Zanesville to Maysville Turnpike and lasted until its demolition in 1886. Originally built as two covered “tied arch” spans with a long trestle approach on the north end, the latter was replaced in 1844 with a covered multiple kingpost truss bridge. Workers, unable to disassemble the bridge, finally burned it. (Ross County Historical Society, Ohio)

The heaviest concentrations of covered bridges, according to Caswell and Kane’s research, were in Pennsylvania, Ohio, and Indiana, though West Virginia and Kentucky appear to have had a great many as well. To illustrate, they have documented 2,068 bridges in Pennsylvania, 4,761 in Ohio, and 598 in Indiana (so far), the earliest in Ohio being 1819 and in Indiana 1831. Beyond Indiana the numbers fall dramatically, and the earliest bridges appear later: 168 for Illinois from the later 1830s, 54 in Missouri from the 1850s, 96 in Iowa from the 1860s. To the north, the numbers fall dramatically: Michigan only 46 from the 1840s, Wisconsin 35 from the 1850s, and Minnesota only 13 from the 1860s.

Going south the numbers tend to decline. Florida is not known to have had any covered bridges. West Virginia had 255 from the 1830s, Kentucky 838 from the 1830s, and Virginia 104 from the same period. Although North Carolina documents only 135 bridges, one is dated to 1818 and South Carolina only 44 but to the 1820s. Interestingly, Georgia and Alabama document 180 and 117 bridge respectively, both from the 1830s, while Tennessee and Mississippi had far fewer, 34 and 12 respectively, from the 1840s.

Once you cross the Mississippi River, there were few covered bridges until you reach the west coast: California had 98 from the 1850s onwards and Oregon 720 from the 1860s. Between Mississippi and California, the few documented bridges were mostly for railroads: 4 in Arkansas after 1840, 8 in Texas after 1850, 13 in Kansas after 1859, 7 in Nebraska after 1879, and a few scattered bridges, mostly on rail lines, in Wyoming, Arizona, and Washington, all from around the turn of the century. Ten states are not known to have had any, including Florida, Louisiana, Oklahoma, the Dakotas, New Mexico, Colorado, Utah, Montana, and Idaho. Surprisingly, however, Alaska had 7 from the 1920s and Hawaii is known to have had at least 2.

Closely related are thousands of open wooden trussed rail bridges built and rebuilt over the decades, virtually all using the Howe truss with its adjustable iron rod verticals. They were built open so as not to capture the smoke and hot ashes from the steam locomotives, but because they were open, they rarely lasted longer than ten years. Although few in number, there were here and there covered aqueducts on the canal systems that developed throughout the Middle Atlantic and Midwestern states in the first half of the nineteenth century. Today, fully covered rail bridges only survive in New England, but in the past they were relatively common in the Midwest and even as far west as Washington State. What percentage of the total number of bridges survives? While it is possible to compute these based on the number of known bridges divided into the number of surviving bridges, the results vary wildly, from 1.5 percent in Kentucky to 23 percent in Washington. For most states where such bridges started early and were built in profusion, the number is in the 2–8 percent range.

Lewis Wernwag’s elegant bridge over the Kentucky River at Camp Nelson in Jessamine County, Kentucky, carried the Lexington Road when it was built in 1838 at a cost of $30,000. A double-lane span 240 feet long, it continued to carry US 27 until a truck broke through the floor in 1926, but the bridge remained until 1933. The Union Army established Camp Nelson in 1863 as a depot to supply its forces in Kentucky and Tennessee. (Wells, 1931: 77)

Hawaii’s few covered bridges, all gone now, were not quite comparable to those on the mainland. This open-sided kingpost bridge, apparently going uphill near Hilo, photographed around 1880 may have been a footbridge. (Hawaii State Archives)

Alaska had perhaps a dozen or so bridges, all of the Western Howe design built after 1900. These “twin bridges” were on the Seward-Anchorage Road in south central Alaska and were removed before 1959. (Alaska State Library)

Spanning Salt Creek at the north entrance to Indiana’s Brown County State Park, the Ramp Creek Bridge was originally built in 1838 just south of Fincastle in Putnam County on what became US 231. This bridge, built by Henry Wolf and Chilion Johnson, is both Indiana’s oldest and its only “double-barrel” bridge. It was moved here in 1932. (A. Chester Ong, 2011)

This historical photo taken in the early 1870s shows Obadiah Wilcox’s 1813 highway bridge over the Sacandaga River near Hadley in Saratoga County, New York. Behind it is a four-span open deck Howe truss bridge carrying the Adirondack Railroad’s first engine, the General MacPherson. The rail bridge was built in 1870 but by 1905 all spans had been replaced. (NSPCB Archives, R. S. Allen Collection)

Using a combination open Post truss, this rail bridge over Clear Creek in Colorado’s Clear Creek Canyon was probably built to serve the state’s gold rush, which began in 1859. The line eventually became the Colorado Central Railroad. (NSPCB Archives, R. S. Allen Collection)

Covered bridges in Canada were mainly built in New Brunswick and Québec. Where Québec began building such bridges in the 1850s and has 1,035 documented crossings, of which 86 survive, and New Brunswick had 454, all built after 1900, with 63 surviving, Ontario had only 11, with 1 surviving today. Oddly, Nova Scotia is credited with 13, with the earliest going back to 1835, but none survive. Far to the west there were perhaps 6 wooden rail bridges, some covered or partially covered, and 1 semi-covered span survives to this day in British Columbia. Today, there are 151 covered/semi-covered bridges listed for Canada out of a historical total of 1,519, or 10 percent.

The Boston and Maine Railroad built and owned most of the covered rail bridges in New England. This one at Bennington, New Hampshire, was built in 1877, probably by David Hazelton (1832–1908), chief bridge engineer for the railroad. Until it was destroyed by fire in 1965, it was the oldest remaining covered rail bridge in the United States. (NSPCB Archives, R. S. Allen Collection)

The Rouge or Sainte-Agathe Bridge spans the Palmer River over a rocky gorge next to Parc de la chute Sainte-Agathe in Québec, Canada. Built in 1928, it is typical of the province’s Town lattice variation. (A. Chester Ong, 2012)

Typical of the covered bridges in New Brunswick, Canada, the Tynemouth Creek Bridge near St. Martins in Saint John County was built in 1927 using a standardized Howe truss. Because it is near the Bay of Fundy, the area is often shrouded in fog. (A. Chester Ong, 2012)