© Iowa Department of Transportation
BH Photo #270820
Although no longer in its original locations, this structure is Wright County's oldest steel truss. The bridge was built across the Iowa River in Section 24 of what is now Grant Township, but prior to 1898 it was part of Belmond Township. The structure was erected in 1877 by local contractor A.S. Leonard using steel supplied by the Wrought Iron Bridge Company of Canton, Ohio. A bridge construction contract was let to Leonard on June 2, 1877, and during that summer he erected the 80-foot truss with a 56-foot approach span. Subsequently, on September 4, 1877, a warrant in the amount of $1,300 issued to Leonard. During much of its existence, the structure was known as the Berry Bridge, named for adjacent landowner James Berry. The truss served in its original location for more than 100 years, until it was replaced in 1986. At that time it was determined eligible for inclusion in the National Register of Historic Places, and documented in accordance with Historic American Engineering Record standards. The main span was then moved to nearby Cornelia Lake Park where it currently spans a small inlet and is used by pedestrians. In the early 1880s, the pin-connected Pratt truss superseded the bowstring arch-truss as the iron bridge of choice for medium-span wagon crossings. Patented in 1844 by Thomas and Caleb Pratt, the Pratt design is distinguished by vertical members acting in compression and diagonals that act in tension. "The Pratt truss is the type most commonly used in America for spans under two hundred and fifty (250) feet in length," noted bridge engineer J.A.L. Waddell wrote in 1916. "Its advantages are simplicity, economy or metal, and suitability for connecting to the floor and lateral systems." Virtually all of the in-state and regional bridge manufacturers marketed the Pratt truss to Iowa's counties. As one of the most active bridge fabricators supplying all-iron spans to the state, the Wrought Iron Bridge Company personified this trend. One of hundreds of bowstrings and trusses erected by WIBCo across the state, the Cornelia Lake Bridge is distinguished as the oldest Pratt pony truss in Iowa. Its subsequent move and alteration have diminished the structure's interpretive value somewhat, but it still remains one of the state's most important early vehicular bridges [adapted from Fraser 1991].