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OVERVIEW OF THE HISTORY OF NEW YORK'S COVERED BRIDGES By Raymond W. Smith Program Analyst for the New York State Office of Parks Recreation and Historic Preservation Throughout much of the nineteenth century, New York was predominately rural; its settlement pattern generally consisted of widely separated communities whose economy was based upon subsistence agriculture and local water-powered industry. Few improved roads connected population centers. As the Empire State grew and its economy expanded, however, road and bridge improvements became essential for linking emerging centers of civic market activity. Covered wood truss bridges of New York State are significant as these structures reflect the history and development of settlement patterns, communities and land-based transportation in new York. The history of covered timber bridge construction in New York State spans the period from the first decade of the nineteenth century to the era of the First World War. The earliest known extant covered bridge was built in 1825; the latest in 1912. Covered bridges are a distinctive property type reflecting vernacular engineering design and construction practice. The earliest permanent bridges in New York were constructed using readily available local materials and skills. Because the cost of constructing bridges generally was the responsibility of local governments, they turned to readily available materials and skills for this purpose. The abundant timber and stone resources found throughout much of New York State made these materials the logical choice for bridge construction during the period of significance. Relative ease of construction was another factor that mitigated in favor of wooden bridge construction. The timber framing skills of local millwrights and joiners were readily adaptable to the construction of timber bridges. During the Colonial period, the first timber bridges incorporated the Kingpost or Queenpost truss configuration. These simple, open structures with plank decks were widely erected across small streams, though their use was limited to clear spans under fifty feet in length. Longer crossings were possible using multiple spans supported by mid-stream piers or timber cribbing. The open timber truss bridge remained an inexpensive and popular form for farm bridges and crossings on minor roads until the early twentieth century, when it was supplanted by the metal span. The open trusswork was sometimes sheathed with protective weather boards to preserve the life of the truss. Because of its horizontal top chord, it was possible to cover a Queenpost truss bridge with a protective roof. The Copeland Covered Bridge (1879), a farmer's bridge in rural Saratoga County, is an extant example of a covered Queenpost truss bridge remaining in New York. From the early decades of the nineteenth century, the cost of building and maintaining timber bridges generally fell upon local governments or state-chartered bridge or turnpike companies, which were established as for-profit ventures. It soon became evident that protecting the bridge's structural system from the elements would reduce the burden of maintenance and replacement costs. This protection was most readily achieved by covering the timber truss bridge with a roof and board sheathing to enclose the frame structure. During the Federal period, inventor Theodore Burr (1722-1822) designed a highly successful long-span bridge form that combined the structural advantages of a simple timber truss with a relieving arch. Burr patented his timber truss design in 1817. His first successful bridge was a four-span structure erected across the Hudson River at Waterford, New York in 1804. Built of hand-hewn pine structural members, the Waterford bridge was sheathed with pine plank siding and covered by a shingled roof. Burr's bridge stood for more than a century until it was destroyed by fire in 1909. The Burr arch truss is represented in New York by three extant historic bridges currently listed in the State and National Registers: Perrine's Bridge (1844), Ulster County; Salisbury Center Bridge (1875), Herkimer County; and Hyde Hall Bridge (1823), Otsego County. A successful truss design nearly contemporary with the Burr truss was the Town lattice truss, patented in 1820 by the versatile builder/architect Ithiel Town (1784-1844). Consisting of a horizontal top and bottom chord connected by a web of closely spaced, alternating diagonal timbers, the Town lattice truss included no vertical members; the required stiffness was achieved by connecting the intersecting diagonals with wood pins. Carried on piers placed at intervals, bridges incorporating the Town lattice truss could span considerable distances. Its inherent strength coupled with its ease of construction made the Town lattice truss design a popular design for highway and early railroad bridges until the post-Civil War era. Listed in the State and national Registers in 1979, the covered bridges at Eagleville (1858) and Shushan (1858), Washington County, are notable examples of the Town lattice truss form. Another notable example of the Town lattice truss, and listed on the Registers in 1998, is the Grants Mills Bridge (1902), Ulster County. During the 1830's Colonel Stephen H. Long (1784-1864) of the U.S. Army Corps of Topographical Engineers perfected a rigid timber truss form that incorporated panels consisting of intersecting diagonals and counters. Long's initial patented design of 1830 for an "assisted truss" included a redundant Kingpost relieving truss above center panel points (where the greatest flex would occur). With practical experience, long refined his design to eliminate its "overbuilt" characteristics, receiving additional patents in 1826 and 1839. The Old Blenheim Bridge (1855), Schoharie County (National Historic landmark, 1964; National Civil Engineering Landmark), is a notable example of the Long truss design. The final major timber truss design to achieve widespread popularity during the late nineteenth century was first patented in 1840 by William Howe (1803-1852). The Howe truss consisted of horizontal timber top and bottom chords and diagonal wood compression members combined with vertical tension members made of wrought iron. The ends of the iron tension rods were threaded and secured to iron shoes at the panel points of the web. The inherent properties of wood and iron as construction materials were effectively used in Howe's truss; this hybrid truss became the most widely constructed, standard American timber bridge form of the nineteenth century. The Rexleigh (1874) and Buskirk (1857) Covered Bridges in Washington County and the Jay Covered Bridge (1857), Essex County, are Howe truss structures listed in the State and National Registers. By the third quarter of the nineteenth century, the covered timber truss bridge was being supplanted by the manufactured metal truss bridge on the roads and rail lines of New York State. Stimulated by wartime growth and development, iron manufacturers turned to production of standardized metal bridge components in the post-Civil War era. The increased strength, ease of construction and reduced cost associated with metal bridges won favor among local governments and railroad companies; by the 1880's, the heyday of wooden bridge-building had passed. Although several examples of covered timber truss spans remain from the early twentieth century in rural areas of new York State, the advantages of iron bridges were clearly understood and widely applied well before 1900. The limited set of covered timber truss bridges that remain in the rural regions of New York State collectively represent a vanishing structure type once common but now increasingly rare. Moreover, the timber framing technology and craftsmanship employed in their construction has largely ceased to be practiced. Because of their increasing rarity and vulnerability, those examples of New York's covered wood bridges that remain substantially intact are eminently worthy of preservation. This document was developed as part of the statewide Covered Bridge Nomination project. |