America's Covered Bridges. Ronald G. Knapp

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