The History of California's Ownership: From Spain to Mexico to the United States

Mexico Never "Owned" California as an Independent Act

The territory that is now California passed through three sovereign claims:

1. Spanish Empire (1769–1821): Colonized via missions, presidios, pueblos. Administered as Las Californias (later Alta California) under the Viceroyalty of New Spain.
2. Mexico (1821–1848): After Mexican War of Independence, Alta California became a Mexican territory (not a state). Secularization of missions (1834), rancho land grants, weak central control.
3. United States (1848–present): Treaty of Guadalupe Hidalgo (1848) ceded California to U.S. after Mexican–American War. Statehood 1850.

Key Clarification

Mexico inherited California from Spain; it did not independently acquire or "own" it in the sense of a voluntary transaction. The 1848 cession was forced by military defeat.

Thus, the premise "When did Mexico own California?" implies a sovereignty that was derivative and brief (27 years), ending by conquest.