The Arizona Territory was created from the western half of the New Mexico Territory during the American Civil War on February 24, 1863.

Four counties (Mohave, Pima, Yavapai and Yuma) were created in 1864 following the organization of the Arizona Territory in 1862.

Arizona has one county that is no longer are in existence. The now defunct Pah-Ute County was split from Mohave County in 1865, but merged back in 1871. 

The Arizona Territory lasted until February 14, 1912, when the territory was admitted as the as the 48th state of Arizona.

All but La Paz County were created by the time Arizona was granted statehood in 1912. Arizona currently is divided into 15 counties. 

Fun Facts about Arizona Counties

County Names

The County names: 8 of them named for Native American Tribes, 2 of them for People, 2 of them for Mountains, 2 of them for Rivers, and 1 of them for a Town.

County Size

  • Coconino County (18,661 sq mi) is the largest county in Arizona.
  • Santa Cruz County (1,238 sq mi) is the smallest county in Arizona.
  • Apache County is the longest county in the country, 211 miles from the Utah border to just south of Alpine.

County Population

  • Greenlee County (7,754) is the least populated county in Arizona.
  • Maricopa County (3,990,181) is the most populated county in Arizona.

Arizona Counties and Cities

Arizona’s 10  largest cities are

  1. Phoenix is in Maricopa County
  2. Tucson is in Pima County
  3. Mesa is in Maricopa County
  4. Chandler is in Maricopa County
  5. Glendale is in Maricopa County
  6. Scottsdale is in Maricopa County
  7. Gilbert is in Maricopa County
  8. Tempe, is in Maricopa County
  9. Peoria is in Maricopa and Yavapai counties
  10. Yuma is in Yuma County

Arizona County Boundary Changes

List of Arizona Counties

List of Extinct Arizona Counties

Pah-Ute County


Pah-Ute County is a former county in the northwest corner of Arizona Territory, created from the division of the existing Mohave County on December 22, 1865.

Much of Pah-Ute County was in the small triangular section of what is now the southern part of the U.S. state of Nevada. The county seat was the town of Callville, which is now occupied by a part of Lake Mead.

Pah-Ute was the historical spelling of the Indian tribe that is today referred to as the Paiute. A short time later, on May 5, 1866, all of Pah-Ute County west of the Colorado River and west of 114 degrees latitude became part of the new state of Nevada, over the protest of the territory of Arizona.

The remaining portion of Pah-Ute County in Arizona was so underpopulated that no viable county government could be formed, and on February 18, 1871, the remainder of Pah-Ute County was absorbed back into Mohave County.

Most of modern Clark County, Nevada, was once Pah-Ute County, Arizona, including Nevada’s largest and most famous city, Las Vegas. To this day, some textbooks still refer to the Pah-Ute as Arizona’s “Lost County”.

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