Year constructed: 1894
Alternate name: Cedar Creek Bridge
Bridge type: Covered Wood Howe Through Truss
National Register of Historic Places status: Listed
Length: 178
feet
Width: 13.3 feet
Spans: 1
FHWA: 238950
Jurisdiction: Marion County
Location: West of 170th Place over North Cedar Creek, 5 miles west of Hamilton, Section 26, T74N-R19W (Indiana Township)
Details
Located some five miles west of Hamilton, this covered bridge carries a seldom-used county road over North Cedar Creek. The bridge is comprised of a timber/iron Howe truss, supported by steel cylinder piers and approached on both ends by steel stringer spans. Known locally as the Hammond Bridge, after nearby landowner Samuel B. Hammond, this structure dates to 1894. In January of that year Hammond approached the Marion County Board of Supervisors with a request for a bridge across the North Cedar River on the road between Attica and Eldorado. After delaying the petition until April, the board examined the site for the proposed bridge and then granted Hammond's request. In June the county contracted with S.F. Collins to erect a "high lattice bridge" at the site on iron tubes, based on a design on file. Presumably, the Hammond Bridge was completed later that year. It has undergone subsequent maintenance-related repairs to the truss's wooden sheathing and replacement and addition of its approach spans, and the stream has been channelized so that the truss is no longer over the main water flow, but the Hammond Bridge still retains a high degree of structural integrity. A truck accident on the bridge in October 1977 closed it for two years and required minor repairs before it could re-open in September 1979. The Hammond Bridge has carried light traffic since that time.
The earliest trusses were comprised entirely of wood. But wood acts poorly in tension, and all-wood trusses such as Theodore Burr's arch-truss featured somewhat inefficient configurations to counteract wood's shortcomings. In 1840 William Howe patented a truss that used timbers for its compression members and iron rods in tension. A significant improvement over the all-wood designs, Howe's trusses were used extensively by the railroads, until a number of collapses in the 19th century (of which the Ashtabula Bridge was the most infamous) directed them toward all-metal designs. Despite these well-publicized disasters involving Howe trusses, counties continue to use them in large numbers for roadway bridge construction in the late 19th century. Iowa once had numerous Howe combination trusses--both covered and uncovered--on its road system. Due to subsequent attrition, however, all but this one span in Marion County have been demolished. The Hammond Bridge is thus technologically significant as the last remaining example in the state of what was once a mainstay structural type [Fraser 1992].