This portion of the route of US 80, predecessor of I-8, was originally part of the proposed state system of highways in 1921. By 1926, this section became part of the cross-country highway US 80. The route was not paved at this time, but was a gravel road along the entire corridor. By 1928, the portion of I-8 between Gila Bend and Casa Grande was designated as SR 84. A small portion of the highway was paved near Yuma and SR 84 was under construction by the next year. SR 84 was completed by 1930, but not paved, and the segment of US 80 between Aztec and Sentinel had been paved.