There are 15 counties in the U.S. state of Arizona. Four counties (Mohave, Pima, Yavapai and Yuma) were formed in 1864 in the Arizona Territory in 1862. All but La Paz County were formed by the time Arizona became a State in 1912.</onlyinclude> There is also one county, Pah-Ute County, Arizona that was formed in 1865 from Mohave County and returned in 1871. 