Each of Arizona's 15 counties has a sheriff, county attorney, county recorder, treasurer, assessor, superintendent of schools, and three or five supervisors, each elected to a four-year term. Counties act as agents of the state.
Other local governmental units are cities, charter cities, and towns (communities with populations under 3,000). Towns generally follow the council-mayor form of government. All of Arizona's largest cities are charter cities. In all, there were 638 local government units in 2002, of which 87 were municipal governments. There were 305 special districts. As of 2002, the state had 245 school systems.
Each of the 21 Indian reservations in Arizona has a tribal council or board with members elected by the people.