America's Covered Bridges. Ronald G. Knapp

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