The Spanish sent priests with almost every mission to the New World, and don't forget Our Lady of Guadelupe, her appearance to Juan Diego spread the faith like fire throughout the SW.
Yep, the construction of Spanish Missions is also why FL had large amounts of Catholics at one time near St. Augustine and Pensacola. There are still some Catholics near St. Augustine, according to the map, but not as many in the Pensacola area these days.