Why were the missions built in Alta California?

Answer 1

"Missions" are / were multipurpose structures used as a form of conquest by the Catholic Church. A few of these purposes were:

• To serve as a 'base' to start towns, act as trading posts, and act as a respite for travelers.
• To act as an indoctrination center to convert local tribes to the religion (while this sounds innocent it was not; it was designed to take the land of the local tribes because of legal blocks put in place around 1532. Unless a majority of the tribe converted the church could not take the land. Even though this dual purpose is well documented the Catholic Church denies it did these things.)
• They also acted, in part, to help Spanish land claims.
  

Answer 2

Why were the mission of Alta California set up