Yuma County is located in the southwestern corner of the state of Arizona. It shares borders with California and Mexico. The county seat and largest city is Yuma. Yuma County is known for its warm climate, agricultural production, and its military installations, such as the Marine Corps Air Station Yuma and the Yuma Proving Ground. Its population was 203,881 in 2020.
The Kofa National Wildlife Refuge is located in Arizona. The refuge, established in 1939 to protect desert bighorn sheep, encompasses over 665,400 acres (2,693 km2) of the Yuma Desert region of the Sonoran Desert.