Tucson remained a military outpost under Spanish and later Mexican control until the area was sold to the United States as part of the Gadsden Purchase in 1853. Tucson was the capital of the Arizona Territory from 1867 to 1877. It was incorporated as a city in 1877. The town grew rapidly when the Southern Pacific Railroad arrived in 1880 and silver and copper deposits were discovered nearby. Tucson is a popular vacation and health resort due to its sunny, mild, dry climate and unique desert location.
Tourism is important to the city's economy.
Major industries include aerospace and missile production, high technology, optics, biotechnology, environmental technology, software, and electronics. Tucson is also the commercial center for the surrounding area's agricultural and mining industries. The city is the home of the University of Arizona.