Yuma Proving Ground (YPG) is a United States Army facility and one of the largest military installations in the world. Situated in southwestern La Paz County and western Yuma County in southwestern Arizona, U.S., approximately 30 miles north-east of the city of Yuma, the proving ground is used for testing military equipment and encompasses 1,307.8 square miles (3,387.2 km²) in the northwestern Sonoran Desert.