In April 1912 a citizens' group petitioned the Navajo County Board of Supervisors for a vehicular bridge over the Little Colorado River at St. Joseph. Typically, the board deferred the matter. In February 1915 another group requested the bridge, but the board again deferred. Finally, in the wake of the Lyman Dam disaster, Navajo County voted a $63,000 bond issue in January 1916 to finance construction of seven bridges damaged or destroyed when the dam broke. The St. Joseph Bridge was one of these. In June the board advertised for the bridges' construction. The following month the county received proposals and designs from eight bridge companies: the Monarch Engineering Company, Miller Construction Company, El Paso Bridge & Iron Company, Canton Bridge Company, Midland Bridge Company, Omaha Structural Steel Works, Mesmer & Rice, and B.Y. Duke. Nebraska-Omaha Structural Steel Works was awarded the contract for the St. Joseph bridge and five other smaller structures for $36,863. For this crossing, Omaha Structural Steel engineered a series of six rigid-connected pony. trusses, supported by concrete-filled steel cylinder piers and flanked on both ends by Umber approaches. The 83-foot trusses used a Pratt configuration, with steel stringers, concrete deck and steel lattice guardrails. Using steel rolled by Lackawanna and Illinois, Omaha Structural Steel fabricated the medium-span trusses, shipped the pieces to the site by rail and erected them the following spring. The St. Joseph Bridge was complete by June 1917. It has functioned as a county-road bridge since. The bridge has more recently been altered by the replacement of its substructure.
Statement of Significance
Before creation of the Arizona Territorial Engineer's office in 1909, vehicular bridges were built either by the counties or by private entities such as toll road operators The state began building bridges immediately after its formation in 1912. Following passage of the Federal Aid Highways Act in 1916, the Arizona Highway Department standardized bridge design and construction, concentrating more on concrete construction than on steel. But in the early years before the highway department controlled bridge design and construction in Arizona, the counties continued to build bridges from their own designs. The St. Joseph Bridge is one of the larger county-built structures in the state-designed, fabricated and erected under contract by a nationally prominent bridge company. The bridge is significant as one of the few multiple-span vehicular trusses remaining in Arizona. Although its substructural replacement has diminished its physical integrity, the St. Joseph Bridge remains an important early example of vehicular truss construction.
Dimensions: Roadway Width: 12.6 Feet; Structure Width: 16.1 Feet; Structure Length: 500 Feet; Main Span Length: 83 Feet.
Substructure: concrete abutments, wingwalls and corrugated steel piers with concrete caps
Floor/Decking: Timber deck with asphalt wheel tracks
Truss Composition: upper chord: 2 channels with cover plate and lacing;
lower chord, vertical and diagonal: 2 angles with batten plates; lateral bracing: 1 angle; floor beam: I-beam; steel lattice guardrails.
Alterations: Substructure replaced and superstructure raised in 1978.