California natives’ lives were reshaped by the mission fathers after 1769, not the townspeople of the pueblos or the soldiers of the presidios. The Franciscans came to California to convert the tribes to Christianity and train them for life in a European colonial society. Conversions were not always voluntary and converts (neophytes) were required to live in settlements sponsored by missions until they were fully trained and converted. They were taught Spanish, the tenets of their new religion and trained in skills for their new lives, like brickmaking and construction, raising cattle and horses, blacksmithing, weaving, tanning hides, etc.
The natives were to live at the missions until their education was complete, and then establish homes in the nearby pueblos. As the native people of one area were Christianized and educated, the missionaries were to move on, leaving the old missions behind to become parish churches as they built new missions in distant locations. The Spanish government nor the Franciscans ever judged any of the natives ready for life outside the mission system, and Christian natives or "Mission Indians" and their descendants remained at the missions until the system was abolished in 1834.
By 1834, sixty-five years of exposure to Europeans had reduced the number of California's native peoples by half to about 150,000. Spaniards introduced not only Christianity, but also new diseases to which the natives had no resistance, and thousands died in epidemics. Crowded, harsh living conditions at the missions contributed to the Indians' health problems, and infant mortality and death rates among young children soared.
Source: The Missions
Library of Congress