Year constructed: 1913-1914
Alternate name: Big Sioux River Bridge
Bridge type: Pin/Rigid-Connected Pratt Through Truss
National Register of Historic Places
status:
ListedÂ
Length: 260 feet
Width: 14 feet
Spans: 3
Jurisdiction: Lyon County
Location: Ashley Avenue over the Big Sioux River, 6.5 miles southwest of Larchwood, Sections 20 & 21, T99N-R48W (Centennial Township)
Details
Located on the outskirts of the small town of Klondike, this long-span through truss crosses the Big Sioux River on the border between Lyon County, Iowa, and Lincoln County, South Dakota. The Klondike Bridge is comprised of a concrete-decked Pratt through truss, with Warren pony truss approach spans on both ends. Concrete abutments and piers support the three trusses. The first bridge was built here in 1901, but as traffic on this regionally important crossing increased over the succeeding years, that structure eventually proved inadequate. In August 1913, the Lyon County Board of Supervisors contracted with the Western Bridge and Construction Company of Omaha, which had built virtually all of the county's trusses for a number of years, to fabricate and erect a replacement structure here. Western began excavating of the concrete substructure soon thereafter and, using steel rolled by the Cambria mills in Pittsburgh, erected the three-span truss later that year. For the pony trusses, Western used the newly developed design standard of the Iowa State Highway Commission. ISHC had not yet engineered a standard for the 160-foot through truss, however, and for this Western apparently used a truss of its own design, featuring both pinned and riveted connections. The structure itself was completed late in 1914, its fills early in 1915. Since its completion, the Klondike Bridge carried interstate traffic in unaltered condition until recently, when it was superseded by another crossing and is now closed to vehicular traffic.
Before the standardization of bridge design in 1913, the individual counties were left to their own devices for bridge construction. Some of the more prosperous counties could afford a full-time staff engineer or could hire consulting engineers for their bridge design but most relied on the bridge companies that bid competitively for bridge construction projects. The Iowa State Legislature changed this process radically when it passed the Brockway Act in the spring of 1913, requiring the counties to use ISHC standards and effectively eliminating the design-build role of the regional and state bridge companies. The proliferation of standard plans occurred quickly in 1913 and 1914, so that the transition period was actually quite brief. In a few cases, though, in which no standard plans yet existed and ISHC did no produce special designs, non-standard structures were approved for construction. This is the case with the Klondike Bridge. Built using both standard and non-standard designs, the Klondike Bridge is historically significant for its representation of this brief transitional period in Iowa highway bridge construction. It is also significant for its role as an important interstate crossing. In well-preserved condition, the Klondike Bridge is an important resource form the formative period of Iowa's highway system [adapted from Fraser 1992].