North Cedar Creek Hammond Covered Bridge – Attica, Iowa
The historic Hammond covered bridge was listed in the National Register of Historic Places in 1998. It is a timber and iron, 8-panel Howe through truss structure with a single, 78-foot long span. Two more modern approach spans bring the total bridge length to 178 feet. The roadway deck width is 13.3 feet. Supporting this superstructure are concrete-filled metal cylinder piers, though the North Cedar Creek channel no longer flows directly between them. Instead, the stream is rechanneled slightly to the north under the longer of the two approach spans. The double-span, 80-foot long north approach to the bridge was added in 1952, though as late as 1956 the creek bed carrying water was still directly under the covered span. The timber deck of Hammond Bridge lays on steel stringers. When the bridge was inspected for the Historic American Engineering Record program in 1992, the following additional physical dimensions and construction techniques were noted: "end post: two 4×8 timber posts; upper chord: three 12×8 timber posts; lower chord: three 12×8 timber posts; vertical: two round rods with threaded ends; diagonal: two 6×8, or 8×8, or one 4×8 timber posts; floor beam: I-beam; gabled wood-frame sheathing, with wood roof shingles and vertical wall planks" (Iowa Historic Bridge Inventory/HAER, 1). Physical inspection in 2003 revealed the walls were covered primarily with barn-plank siding applied vertically. Some of the 10- to 12"- wide plank siding was probably original but the lower ends were badly weathered and deteriorated. Underneath the sheathing, joinery of the truss wood members was both by notching and bolts.
According to one bridge historian, the Howe truss wagon road bridge was once much more common in Iowa, with counties erecting them long after railroads abandoned the wood-based truss for stronger metal structures. William Howe patented his truss design in 1840, using timbers for the compression members combined with iron rods in tension. In Iowa, the Hammond Bridge is the last Howe truss road bridge, covered or uncovered, remaining (Iowa Historic Bridge Inventory/HAER, 2).
Location: 170th Place, south of Attica, just off G-76