Dietzenbach Bottom Bridge

Information and Findings From Iowa's Historic Bridge Inventory

Discussion of Bridge

This single-span truss crosses the Turkey River at the northern edge of Fayette County, in Section 3 of Auburn Township. Known locally as the Mill Race Bridge, presumably for its proximity to a riverside mill, the structure is configured as a six-panel Warren truss with pinned connections. The existing concrete abutments are evidently replacements of an earlier substructure. Although county records are somewhat sketchy, the Mill Race Bridge appears to have been erected n 1890. In January of that year the county board of supervisors received a citizens' petition for a permanent bridge at this location. The petition was referred, along with six others, to a committee of the whole, after which a contract was awarded to build the bridge. Fayette County had dealt almost exclusively with Horace E. Horton, a brilliant civil engineer from Minneapolis, for its wagon bridges in the 1880s. When Horton moved to the Chicago Bridge and Iron Company in the late 1880s, he brought the county with him as a client, and the latter firm was largely responsible for the county's bridges in the 1890s. The Mill Race Bridge was probably fabricated and erected by Chicago B&I for the county in 1890. Other than the subsequent replacement of its substructure, it remains in essentially unaltered condition today.

The Pratt and Warren truss configurations were both developed in the 1840s, but it was the Pratt that received the most widespread use in the late 19th century. The reasons for this probably relate to the versatility of the pin-connected Pratt for different span lengths and its easier erection using timber falseworks. Relatively few pinned Warren trusses were ever built in Iowa and only a handful remains in use today. The Mill Race Bridge is distinguished as a well-preserved example of this uncommon 19th century truss type [adapted from Fraser 1992].

Bridge Considered Historic By Survey: Yes