Interstate 10 in Arizona 2013. The remainder of the old US 80 section was rebuilt to interstate standards, with completion in 2014. East of Tucson, I‑10 parallels and in some cases overlies old US 80 to Benson, and was originally co-signed as US 80 and SR 86. The section of I-10 from Valencia Road to Rita Road was the first construction project in the state of Arizona funded by the Federal Aid Highway Act of 1956. Construction began in 1957 and was completed in 1960. From Benson, the Interstate follows the Southern Pacific mainline east through Willcox and Bowie to New Mexico, rather than
Arizona State Route 66 line, much of US 66 has been replaced with I-40. Various stretches of the old highway exist as frontage roads and business loops of I-40. In 1984, US 66 was officially removed from the state highway system of Arizona. Most of the old highway had been replaced by I-40, but the portion between Kingman and Seligman where I-40 followed a new alignment to the south became SR 66. In 1990, the state turned over the easternmost of SR 66 (known as Crookton Rd) to Yavapai County for maintenance. Arizona State Route 66 State Route 66 (SR 66) is a surface