Year constructed: 1913
Bridge type: Concrete Filled Spandrel Arch
National Register of Historic Places status: Listed
Length: 47 feet
Width: 20 feet
Spans: 1
FHWA: 316480
Jurisdiction: Story County
Location: 550th Avenue over Keigley Branch, 3.2 miles northeast of Gilbert, Section 35 & 36, T85N-R24W (LaFayette Township)
Details
When the Iowa State Highway Commission was re-formed in 1913, the agency immediately began developing standard designs for small-scale bridges. Denouncing the patented filled spandrel arch of Indianapolis engineer Daniel Luten as structurally unsound, ISHC engineers designed an alternative arch. With its elliptical profile and bundled reinforcing, however, the highway commission's arch differed only by degree from Luten's earlier design. Numerous examples of these arches were built in the 1910s and 1920s throughout the state. The Keigley Branch Bridge in Story County is distinguished among these as the earliest remaining ISHC-designed arch. It was built in 1913 by the county under contract with the Koss Construction Company of Des Moines. Costing $3,384.85, the bridge consisted of a medium-span arch, with ISHC standard, paneled concrete guardrails, a corbelled arch ring, and bi-chrome concrete detailing. The Keigley Branch Bridge has carried vehicular traffic since its completion in 1913, in unaltered condition [adapted from Fraser 1992].