Tempe Historic Property Survey

The Tempe State Bridge, better known as the Ash Avenue Bridge, was the first major highway bridge crossing the Salt River. When construction began in 1911, labor was provided by prisoners from the Arizona Territorial Prison in Florence. The bridge was completed in 1913. It provided the first dependable crossing between Phoenix and Tempe and Mesa for wagons and automobiles. Unfortunately, the bridge was obsolete by the time it opened. It had been designed more for wagons than for automobiles, and it was too narrow to carry two lanes of traffic. In 1916, a flood weakened one of the supporting arches and seriously damaged the bridge. After the Arizona Highway Department built a new bridge (the Mill Avenue Bridge) in 1931, the Ash Avenue Bridge was no longer used.

The Tempe Concrete Arch Highway Bridge was an 11-span reinforced concrete open spandrel rib arch bridge that crossed the Salt River at Tempe. The design for the Tempe bridge employed ten piers anchored to the bedrock below the streambed. Every third pier was constructed on a solid bottom concrete abutment type. The intermediate piers were anchored on two concrete filled steel cylinders six feet in diameter driven into the bedrock. There were ten 125-foot long open spandrel rib arches and each consisted of two three-hinged segmented arch ribs placed 13 ft. on center. The reinforced concrete deck was carried by 12-inch by 12-inch concrete spandrel columns placed 11 feet on center and connected at the top by semicircular spandrel arches. On the exterior side of the spandrel columns were semi-spandrel arch brackets cantilevered out from the columns to carry the curb and desk balustrades. It was designed to carry a 15-ton tractor engine and a live load of 100 pounds per square foot.

The Tempe Concrete Arch Highway Bridge, built 1911-1913, was the oldest surviving multiple arch concrete bridge in Arizona. It was also significant as one of the first major bridges built by the Territory of Arizona and as the first large highway bridge across the Salt River. As the first automobile bridge between Phoenix and Tempe, this structure provided a vital link between Phoenix and communities to the south. It was also significant in the development of Tempe during its two decades of service as a major highway route across the river.

In 1909, the State of Arizona began to develop a north-south highway system and the need for a bridge at the Salt River became apparent. That year, the Territorial Legislature appropriated funds for the construction of a highway bridge at Tempe. Preliminary work began in the spring of 1911 on an alignment approximately 500 feet east of the 1905 Arizona Eastern Railroad Bridge. When construction began in 1911, labor was provided by prisoners from the Arizona Territorial Prison at Florence. Although convict labor had been used on earlier projects, this bridge is one of the last remaining examples of construction accomplished under that system. Although Roosevelt Dam was completed in 1911, flooding of the Salt River was still a fairly common experience, and periodic repairs (1916, 1920,and 1925) were necessary to maintain safe conditions on the bridge. By the late 1920s, automobiles became wider, heavier, and more numerous, stressing the structure beyond its design limits. In 1928 the Arizona Highway Department recommended the construction of a new river crossing and in 1931, when the new structure (HPS-226, Mill Avenue Bridge) was complete, the 1911 bridge was closed to all but pedestrian traffic.

The Ash Avenue Bridge was demolished in 1991 because it would have cost too much to repair the structural damage that it had suffered. Only a segment of the bridge at the south abutment was saved. The current listing on the National Register should be amended to redefine it as a standing ruin.

Go to the Tempe Historic Property Survey