Tucson is the seat of Pima County, Arizona, United States, located 118 miles (188 km) southeast of Phoenix and 60 miles (98 km) north of the U.S.-Mexico border. As of July 1, 2006, a Census Bureau estimate puts the city's population at 525,529, with a metropolitan area population at 1,023,320 as of July 1, 2008. In 2005, Tucson ranked as the 32nd largest city and 52nd largest metropolitan area in the U.S. It is the largest city in southern Arizona and the second largest in the state. Tucson is also the site of the University of Arizona.
Major incorporated suburbs of Tucson include Oro Valley and Marana northwest of the city, and South Tucson and Sahuarita south of the city. Communities in the vicinity of Tucson (some within or overlapping the city limits) include Casas Adobes, Catalina, Catalina Foothills, Flowing Wells, Green Valley, Tanque Verde, New Pascua, Vail and Benson.
Jesuit missionary Eusebio Francisco Kino visited the Santa Cruz River valley in 1692, and founded the Mission San Xavier del Bac about 7 miles (12 km) upstream from the site of the settlement of Tucson in 1700. The Spanish established a presidio (fort) on August 20, 1775 and the town came to be called "Tucson". Tucson became a part of Mexico after Mexico gained independence from Spain in 1821. Following the Gadsden purchase in 1853, Tucson became a part of the United States of America, although the American military did not formally take over control of the community until March 1856. From August 1861, until mid-1862, Tucson was the capital of the Confederate Arizona Territory. Until 1863, Tucson and all of Arizona was part of New Mexico Territory. From 1867 to 1879, Tucson was the capital of Arizona Territory. The University of Arizona, located in Tucson, was founded in 1885.
By 1900, 7,531 people lived in the city. At about this time, the US Veterans Administration had begun construction on the present Veterans Hospital. Many veterans who had been gassed in World War I and were in need of respiratory therapy began coming to Tucson after the war, due to the clean dry air. The population increased gradually to 13,913 in 1910, 20,292 in 1920, and 36,818 in 1940. In 2006 the population of Pima County, in which Tucson is located, passed one million while the City of Tucson's population was 535,000.
During the territorial and early statehood periods, Tucson was Arizona's largest city and commercial area, whereas Phoenix was the seat of state government and agriculture. The establishment of Tucson Municipal Airport increased its prominence. By the 1920s-30s, Phoenix outgrew Tucson and has continued to expand. Tucson has still been growing but at a slower pace.