The bridge was constructed to bypass a concrete apron through the river in front of the Gillespie Dam, which was often closed due to flooding.

From its opening until 1956, the bridge was part of U.S. Route 80 (US 80), a transcontinental highway between San Diego, California and Tybee Island, Georgia.

Between Yuma and Phoenix, a section of highway 200 miles (320 km) long traveled through Dome and Wellton before crossing to the north side of the Gila River, and passing through Agua Caliente, Arlington and Buckeye.

[4] In 1912, state highway engineer Lamar Cobb began planning the construction of a dedicated bridge across the Gila River, surveying potential sites near Antelope Hill and Dome.

[6] While the concrete girder design made it stronger against automobiles than a steel bridge, it was weaker against the heavy forces of desert flash flooding.

However, when river conditions proved temperamental or treacherous, the apron was either shut down or several cars had to be tied together into a long train before crossing.

[4] Three years after the construction of the concrete apron, the Arizona Highway Department began planning for a dedicated bridge again.

Highway Department engineer Ralph Hoffman worked with Leeson to design a multiple span Camelback through truss bridge.

The Lee Moor Construction Company of El Paso, Texas, won the contract for quoting the lowest of all potential bidders.

It was severe enough to close the US 80 dam apron for six days, and caused large amounts of equipment and materials needed for the bridge construction to be washed away.

Despite constant modernization, the Gillespie Dam Bridge remained part of mainline US 80 until 1956, when a new alignment was built to the east.

However, due to its strong steel truss design and the fact the concrete support piers were sunk into the bedrock, the bridge didn't collapse.

[11][12] The project included strengthening of the concrete piers and steel truss sections, as well as replacement of the roller bearings and construction of the Gillespie Dam Interpretive Plaza.

[1][14] On September 21, 2018, the Gillespie Dam Bridge along with Old US 80 Highway were designated as part of Historic U.S. Route 80 by the Arizona Department of Transportation.