Arizona is a landlocked state in the Southwestern region of the United States. Arizona is part of the Four Corners region with Utah to the north, Colorado to the northeast, and New Mexico to the east; its other neighboring states are Nevada to the northwest, California to the west and the Mexican states of Sonora and Baja California to the south and southwest. It is the 6th-largest and the 14th-most-populous of the 50 states. Its capital and largest city is Phoenix.

Baja California, officially Estado Libre y Soberano de Baja California, is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of Baja California. It has an area of 70,113 km2 (27,071 sq mi) and comprises the northern half of the Baja California Peninsula, north of the 28th parallel, plus oceanic Guadalupe Island. The mainland portion of the state is bordered on the west by the Pacific Ocean; on the east by Sonora, the U.S. state of Arizona, and the Gulf of California; on the north by the U.S. state of California; and on the south by Baja California Sur.