The main purpose of the Spanish Mission system in California was to spread Christianity among the Native American population and to establish Spanish territorial claims in the region. Initiated in the late 18th century, the mission system aimed to convert indigenous peoples to Catholicism, promote agriculture, and cultivate European cultural practices. The missions served as religious, cultural, and economic centers, fostering the development of towns and settlements. However, the system also led to significant disruption of Native American societies, as forced labor and disease decimated their populations, resulting in profound cultural and demographic changes.