A 2003 report by the state of California indicates that the primary intent of Spanish Missions and forts was to expand European "ownership" of lands in North America and to protect the presumed "ownership" from encroachment by other Europeans. Spanish Period (1769-1822) "Exploration of California first occurred in 1540 when a land expedition under the command of Hernando de Alarcon traversed inland along the Colorado River. Two years later, Juan Rodriquez Cabrillo was commissioned by the Spanish government to investigate the western shores of the newly acquired territory.
In the following two centuries, little interest was given to California. By the late 18th Century, European political powers created renewed interest in California. Military "explorers" from Great Britain, France and Russia began investigating the resources along the western shores of the entire North American continent. The Spanish government, realizing that settlement by any of these foreign parties north of Mexico could become a threat, decided it was time to establish their own settlements in California.
In 1769, plans were put in place to found a series of forts (presidios) and Catholic missions along the Alta California coast extending as far north as Monterey Bay... Over the course of the next half-century, four presidios, twenty missions and three towns were established. The forts were located at San Diego, Santa Barbara, Monterey and San Francisco. The towns were founded at Los Angeles (1781), San Jose (1777) and Branciforte (1797), near Santa Cruz." — SCAG — Southern California Association of Governments, Cultural Resources DRAFT 2004 Regional Transportation Plan (RTP) Progam Environmental Impact Report (PEIR), December 2003