Five missions were established along the San Antonio River from 1718-1731. This became the largest concentration of the Catholic missions in North America, Mission Concepcion, Mission San Jose, Mission San Juan, Mission Espada and Mission de Valero (the Alamo). They were primarily built to expand New Spain (now known as Mexico). The idea was to introduce Native Americans to Spanish society and convert them to Catholicism.
Today the churches still have active congregations, holding mass, performing marriages, baptisms, and funerals. In early 2006, San Antonio began the process of having the missions recognized by UNESCO, the United Nations Educational, Scientific and Cultural Organization, and on July 5, 2015 UNESCO designated the San Antonio Missions as a World Heritage site.
If you're ever in the San Antonio area I encourage you to visit Mission Trail. These places are rich with history and extremely beautiful.