page_title: Gillespie Dam Bridge
section_title: History
hierarchical_section_title: Gillespie Dam Bridge / History
caption_attribution_description: English: The historic Gillespie Dam Bridge marker. The historic Gillespie Dam Bridge was built in 1927 over the Gila River and is located on Old Highway 80 north of Gila Bend and south of Arlington between the Buckeye Hills and the Gila Bend Mountains in Maricopa County. The bridge was at the time the longest highway bridge in the state of Arizona. The bridge was listed on the National Register of Historic Places on May 5, 1981, reference #81000136
context_page_description: The Gillespie Dam Bridge is a through truss bridge spanning the Gila River in Maricopa County, in the U.S. state of Arizona. 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. Construction of the bridge started in 1925 and completed in 1927. From its opening until 1956, the bridge was part of U.S. Route 80, a transcontinental highway between San Diego, California and Tybee Island, Georgia. The bridge was restored in 2012 by Maricopa County for the Arizona Centennial and now includes an educational interpretive center for visitors. The bridge became part of Historic US 80 in 2018.
context_section_description: The Ocean-to-Ocean Highway was established in 1911 after delegates from California, Arizona and New Mexico met in Phoenix. The purpose of the new route was to establish an all weather transcontinental highway through the state and two territories. 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. Maintenance of the route was originally split between Yuma and Maricopa counties.
  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. Ultimately, the Antelope Hill location won out. Construction on the timber and concrete girder Antelope Hill Highway Bridge began in 1914. The bridge measured 1,000 feet (300 m) in length. Originally the state wanted to use prison labor to construct the bridge, but had instead let Cobb hire out construction work to an individual named Perry Borchers. The construction process however was anything but routine. After beginning work on the bridge in June 1914, Borchers defaulted and a flood the following winter badly damaged the incomplete bridge. The state returned to the original solution of using unpaid prisoners and finished the bridge in 1915. Between 1917 and 1923, the Ocean-to-Ocean Highway became part of the Dixie Overland Highway, Bankhead Highway and Old Spanish Trail auto trails.
  However, problems began to plague the Yuma to Phoenix section of the Ocean-to-Ocean Highway. Not only was the highway between Antelope Hill and Arlington built on weak soil, but on the Gila River floodplain as well.  A flood on November 24, 1919 badly damaged the highway as did a second flood in February 1920. Flooding was also taking its toll on the Antelope Hill Bridge, with the structure being washed out every time a large flood happened. The timber approach trestles had to be replaced every time and the concrete sections constantly repaired. 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. Furthermore, the bridge was built on one of the most turbulent sections of the river.
  Due to the mounting problems, the Arizona Highway Department decided in 1920 to re-route the Ocean-to-Ocean Highway between Wellton and Arlington south of the river through Gila Bend. But due to Arlington being on the north side of the Gila River, a new crossing of the Gila would have to be established. An odd solution came in the form of agricultural businessman Frank A. Gillespie and the Gillespie Land and Irrigation Company. In 1921, Gillespie and his company constructed the Gillespie Dam, a concrete irrigation dam, spanning the Gila River. After plans for a bridge across the dam fell through, the Highway Department decided instead to build a temporary concrete apron at the foot of the dam to allow cars to drive through the river until the state could build a dedicated bridge across the GIla. The apron was completed and opened to traffic in 1922. 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.
  Three years after the construction of the concrete apron, the Arizona Highway Department began planning for a dedicated bridge again. Preliminary survey work by means of sounding and boring was conducted in April 1925. The Highway Department consulted bridge engineer R.V. Leeson of the Topeka Bridge and Iron Works for advice. Due to the recurring problems the state of Arizona had with concrete girder bridges, Leeson suggested the state turn to building a multiple span steel through truss bridge instead. Highway Department engineer Ralph Hoffman worked with Leeson to design a multiple span Camelback through truss bridge. The abutments and piers would reach 25 feet (7.6 m) below the riverbed into solid bedrock. The deepest pier would reach
caption: A welcome sign for the Gillespie Dam Interpretive Plaza.
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