For 10 points, name this city acquired by the U.S. in the Gadsden purchase, currently the largest city in the former Gadsden territory, which is home to Davis-Mothan Air Force Base, the Kitts Peak Observatory, and the Insight.
The mission in this city, San Xavier del Bac, opened in 1700 and the town was permanently settled in 1776.  Its name comes from a Papago word meaning "village of the dark spring at the foot of the mountain," and it is ringed in by four different mountain ranges: Rincon, Santa Catalina, Santa Rita, and the namesake range.  For 10 points, name this city acquired by the U.S. in the Gadsden purchase, currently the largest city in the former Gadsden territory, which is home to Davis-Mothan Air Force Base, the Kitts Peak Observatory, and the Insight.Com Bowl at the University of Arizona stadium?
The mission in this city, San Xavier del Bac, opened in 1700 and the town was permanently settled in 1776.  
Tucson, AZ