Yumacity, seat (1871) of Yuma county, southwestern Arizona, U.S. It is situated on the Colorado River at the mouth of the Gila River, just north of the Mexican frontier. Founded in 1854 as Colorado City, it was renamed Arizona City (1862) and Yuma (1873), probably from the Spanish word humo, meaning “smoke,” because of the local Quechan (Yuma) practice of creating smoke clouds to induce rain. A strategic river crossing, the site was probably visited in 1540 by Hernando de Alarcón (working with the Coronado expedition).

Yuma is the centre of large irrigation districts that have transformed parts of the desert into rich farmland. Thus, agriculture, tourism, and some light manufacturing form the basis of the economy, which is augmented by the nearby Yuma Proving Ground (1942), the Marine Corps Air Station (1928), federal and local government centres, and the two-year Arizona Western College (1962). Yuma Territorial Prison (1876), now a state historical park, displays artifacts and photographs of prison life in the old West. Inc. town, 1871; city, 1914. Pop. (19902000) city77, 54,923515; Yuma MSAMetro Area, 106160,895026; (20002010) city93, 77,515064; Yuma MSAMetro Area, 160195,026751.