Was California Ever Part of Mexico? Yes (1821–1848)

Yes. California was part of Mexico for 27 years.

Timeline

• 1769–1821: Spanish colony (Alta California) — missions, presidios, pueblos.
• 1821: Mexico wins independence from Spain; Alta California becomes Mexican territory.
• 1821–1846: Mexican era — secularization of missions, rancho land grants, foreign traders (US, UK, Russia), growing American immigration.
• 1846–1848: Mexican–American War. US forces occupy California (Bear Flag Revolt, Commodore Sloat, Stockton, Frémont, Kearny).
• 1848 (Feb 2): Treaty of Guadalupe Hidalgo — Mexico cedes California (plus NV, UT, AZ, NM, CO, WY) to US for $15M.
• 1850 (Sep 9): California admitted as 31st state (free).

Legacy

Spanish/Mexican heritage permeates California: place names (Los Angeles, San Francisco, San Diego, Sacramento), architecture, law (community property, water rights), culture, and demographics.