Walnut Canyon Bridge, Winona, Arizona. In 1922, the United States Bureau of Public Roads undertook a 23-mile road-building project along the Winslow Highway that stretched between Flagstaff and Angel through the Coconino National Forest in Arizona. The largest structure built as part of the project was the Walnut Canyon Bridge, which spans the canyon crossing Walnut Creek one mile northwest of Winona. Soon after completion in 1924, the road and the bridge became part of Route 66.
The bridge employs a straightforward design. It has a single span of 101 feet and a 19-foot-wide roadbed. The superstructure is of riveted steel and uses a five-panel Parker through truss. Truss bridges have a combination of members, usually arranged in a triangular configuration, to form a rigid framework. A Parker truss includes an additional element: an upper polygonal chord. The substructure has concrete abutments and wing walls. The floor is a concrete deck over steel stringers. The bridge has steel lattice guardrails with concrete curbs. The design and materials were efficient.
While the Walnut Canyon Bridge represents common construction of its time, it is now a rare surviving example on Route 66. The bridge is closed to traffic, but remains intact on a short stretch of abandoned roadbed. The National Park Service listed the Walnut Canyon Bridge in the National Register of Historic Places in 1988.
Tags: Winona Arizona AZ Route 66 Bridge Walnut Canyon Parker Truss Steel National Register Historic Places NRHP
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