Tooele (tōĭlˈə) [key], city (1990 pop. 13,887), seat of Tooele co., N central Utah, a rapidly growing suburb of Salt Lake City, in a farm area; inc. 1853. A major source of employment is the Tooele Army Depot, a huge installation that includes the Dugway Proving Ground; chemical weapons storage and disposal facilities are also nearby. Tooele has a large copper-mining industry; the Elton Tunnel (4 mi/6 km long; built 1937–42) in the Oquirrh Mts. leads to the source of the ores in Bingham Canyon. The city was settled (1849) by Mormons on a California wagon route. Of interest are the remains of stops on the pony express.