There are several extremely rare and significant pin-connected truss bridges on the lower section of the Des Moines River. Each are distinguished as rare surviving examples of large, multi-span examples of their type. Among them, the Kilbourne Bridge stands out for the large number of spans (six). It is a traditionally composed truss with a-frame portal bracing. Each span contains nine panels. The bridge also appears to retain good historic integrity. Most of the surviving Des Moines River pin-connected truss bridges in this region remain inaccessible due to flooding and deck damage. The Kilbourne Bridge is one of those bridges. At least from the south, the bridge is inaccessible due to the approach being washed out from the bridge by flooding. Available time did not allow for an investigation from the northern approach to this bridge. As such, the HistoricBridges.org documentation of this bridge is incomplete. Overview photos are available for this bridge, but only a few detail photos are available. Be sure to review the HAER page for this bridge for additional detail and on-bridge photos.
HAER notes that the bridge is historically significant as the first major project undertaken by the newly formed State Highway Commission. It is also a representative example of the only state standard pin-connected truss design that the commission designed. In 1913, they switched to a plan for truss spans with riveted connections.
Below is a thumbnail link to a cropped HAER photo of the plaque from this bridge.
Information and Findings From Iowa's Historic Bridge Inventory
Discussion of Bridge
In June 1890 the Van Buren County Board of Supervisors inquired into the possible construction of a bridge across the Des Moines River at the Kilbourn ferry crossing. After taking soundings and measurements, the county contracted with the Western Bridge Company of Chicago to build a structure for an estimated cost of $14,950. This bridge stood only 13 years before it was destroyed by flooding on the river in 1903. The following spring, area residents petitioned the board for a replacement structure but the board took no action until January 1907. Construction for a new structure was authorized, with a price tag not to exceed $20,000. The first bid opening, in June 1907, failed with all bids coming in over the not-to-exceed amount. County citizens tried, but did not succeed, to raise funds to meet the low bid, prompting the supervisors to defer the issue until the following year. Eight months later the board determined that changes to the bridge's design were necessary, and the Iowa Sate Highway Engineer was consulted to develop new plans. The new design was approved, and the job again opened for bidding, this time without the $20,000 limit. The county awarded the $23,400 contract in June 1908 to the Ottumwa Supply and Construction Company of Ottumwa, Iowa, for construction of the superstructure and concrete piers. After several delays in construction, the Kilbourn Bridge was finally completed in December 1909, more than six years after the destruction of the earlier structure. It has since carried vehicular traffic over the Des Moines River on a north-south county road.
In its formative years before the passage of the Brockway Act in 1913, the Iowa State Highway Commission played a relatively minor role in bridge design and construction. ISHC engineers at this time concerned themselves principally with small-scale demonstration projects designed to show the utility of concrete for bridge construction. But the highway commission undertook a small number of major bridge commissions as well, the largest and most noteworthy of which was the Kilbourn Bridge in Van Buren County. The Kilbourn Bridge is thus historically significant as the first large-scale engineering project undertaken by ISHC. Indicative of its transitional nature, it is also one of the only pin-connected truss designs the ISHC used prior to adopting its standard, rigid-connected truss plans in 1913. A regionally important crossing of a major river, the Kilbourn Bridge is an outstanding, well-preserved example of wagon truss construction - one of the last of the multiple-span pinned trusses remaining in Iowa [adapted from Fraser 1991].
Bridge Considered Historic By Survey: Yes
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