In 1864, the first Territorial Legislature stimulated road development by authorizing toll road companies. The Legislature also declared that certain existing roads, developed solely by usage, were free county roads not subject to tolls. Subsequently, the Legislature authorized counties to levy a road tax for construction. The counties did most of the construction even after the appointment of a Territorial Engineer in 1909 and the establishment of the Office of State Engineer at the time of statehood in 1912.
The Legislature formed the Arizona State Highway Department and established the Arizona State Highway Commission in 1927. The Arizona Department of Transportation (ADOT) was organized in 1974 by combining the Arizona Highway Department and the Arizona Department of Aeronautics. A seven member Arizona State Transportation Board became its governing body.
The Arizona Department of Transportation (ADOT) under state law is responsible for constructing and maintaining all interstate and state highways in Arizona and providing financial assistance to public airports for airport development projects.
The Intermodal Transportation Division (ITD) is responsible for carrying out this responsibility for the Department and requires an extensive public participation process and technical evaluation effort known as the priority programming process. This process culminates in the Five-Year Transportation Facilities Construction Program for Highways and Airports. This program emphasizes meeting pavement preservation needs on the interstate and non-interstate highway systems and continuing funding for projects in corridors that were started in previous five-year programs.