The Spanish explorers first arrived in the modern-day US State of California (then called Alta California) by land in 1540 (Hernando de Alarcón ascended the Colorado River). A few years later they came by sea – Juan Rodríguez Cabrillo explored the coast in 1542. After that not a lot happened, in terms of the migration of Spanish people (or subjects of the empire) for a few hundred years.

In 1769 the Sacred Expedition was launched, moving religious servants north into Alta California by land and sea. That same year Father Junípero Serra dedicated the mission at San Diego de Alcalá (in the area which later became the modern city of San Diego).

Captain Juan Bautista de Anza was chartered with finding a land route from Northern Mexico into Alta California. His first expedition in 1774 was exploratory and during his second he brought more military and civilian people, including families, as well as large numbers of animals.

Where the new arrivals would live in California was generally one of three types of settlements: religious (misiones in Spanish or missions in English), civilian (pueblos or towns) or military (presidios or forts).

The general idea of the missions in California was to teach the native people the ways of God, to become so-called gente de razón (people of reason). Once that happened the large swaths of land that the missions claimed and were holding in trust for the native people, was to be given over to the now-converted natives. While many native people attended the missions – learning, laboring, adapting and in fact dying there – very few ever received the land that was promised.

Two of the most populous cities in the western United States, San Jose (founded in 1777) and Los Angeles (1781) began as pueblos during Spanish rule in California. Pueblos were secular townships that offered a safe place to live. After all, these settlers were on the edge of the Spanish empire. Pueblos stood in contrast to the religiously-driven missions and military-controlled presidios. Additional pueblos were established in San Francisco (then called Yerba Buena) and Santa Cruz (Branciforte).

The presidios (military forts), in California had the dual purpose of defending Spanish land claims against foreign governments and protecting the missions (and sometimes the pueblos). During the California mission era, presidios were established at San Diego, Monterey, San Francisco (now a national park and major public outdoor space) and Santa Barbara. A fifth presidio was later established in Sonoma for the purpose of discouraging further Russian settlements.