Tucson ([tuːsɒn] en anglais) est une ville des États-Unis, la deuxième en importance de l'État de l'Arizona après la capitale, Phoenix. La ville se situe à 188 km au sud de Phoenix et à 98 km de la ville de Nogales, le long de la frontière américano-mexicaine. D'après le recensement fédéral de 2010 (Bureau du recensement des États-Unis), sa population était de 520 116 habitants et l'agglomération 980 263 habitants ce qui en fait la 33e ville et la 52e métropole des États-Unis. Tucson est le siège du comté de Pima et de l'Université d'Arizona.
Mission San Xavier del Bac is a historic Spanish Catholic mission located about 10 miles (16 km) south of downtown Tucson, Arizona, on the Tohono O'odham San Xavier Indian Reservation. Named in 1692 by Padre Eusebio Kino for a pioneering Christian missionary and co-founder of the Society of Jesus (Jesuit Order), the Mission is also known as the "place where the water appears," as there were once natural springs in the area. The Santa Cruz River which now runs only part of the year is also nearby. The Mission is situated in the center of a centuries-old Indian settlement of the Tohono O'odham (formerly known as Papago), located along the banks of the Santa Cruz River.
The Mission is a pilgrimage site with thousands of pilgrims who visit the church each year many of them walking or riding on horseback cabalgatas.