A short history
The Tohono O'odham and their ancestors farmed this valley for thousands of years, giving Tucson a claim to be one of the oldest continuously inhabited areas in North America. Spanish missionaries arrived in the 1690s, and Mission San Xavier del Bac was completed in 1797. The Spanish built a presidio in 1775, and the area passed to the US in the 1854 Gadsden Purchase. Railroads, military bases and the University of Arizona later shaped the modern city.