Turkey River Bridge
National Register of Historic Places status:
State Street over the Turkey River in Eldorado, Section 7, T95N-R8W (Dover Township)
Located in Eldorado, this medium-span truss carries an unpaved county road over the Turkey River;. Known locally as the Eldorado Bridge, the structure consists of a single pin-connected Camelback through truss, supported by stone abutments. The Eldorado Bridge was constructed by contractor J.G. Ratcliff of Waukon, Iowa, under contract with the Fayette County Board of Supervisors. Completed in March 1899, it has functioned in place since, in essentially unaltered condition.
Straight-chorded Pratt through trusses were used extensively throughout Iowa for medium-span crossings in the late 19th and early 20th centuries. For longer crossings after the turn of the century, however, bridge companies could develop greater efficiency with polygonal-chorded Pratt variants--primarily Parker, Pennsylvania and Camelback trusses. With its distinctive five-faceted upper chords, the Camelback configuration was disdained by some engineers (including the venerable J.A.L. Waddell, who called it "uncompromisingly ugly") for its tendency under certain conditions to reverse compressive and tensile forces acting on their individual members. As a result, Camelback trusses have never received widespread acceptance. Relatively few were ever built on Iowa's roads, and only a handful has been identified as extant by the bridge inventory. The Eldorado Bridge is this technologically significant as a well-preserved example of this uncommon structural type [adapted from Fraser 1992].