Arizona is a state in the southwestern region of the United States. It is also part of the Western and the Mountain states. It is the sixth largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona, one of the Four Corners states, is bordered by New Mexico to the east, Utah to the north, Nevada and California to the west, and Mexico to the south, as well as the southwestern corner of Colorado. Arizona's border with Mexico is 389 miles long, on the northern border of the Mexican states of Sonora and Baja California.