| 1821 | Mexico declares independence from Spain. Luis Arguello explores the Sacramento Valley. |
| 1822 | Mexican authority extended into California. Alta Californians elect their first provincial legislature, which meets in Monterey. Luis Arguello is elected Governor. |
| 1823 | Mission San Francisco Solana is founded. Mission revolt in the central region. |
| 1824 | Mexican Emperor Iturbide's dominion falls and is replaced by a republic. The Mexican Congress establishes rules for land grants and colony promotions, giving preference to Mexican citizens. |
| 1825 | California joins the Mexican Republic. Antonio María Osio, who will write History of Alta California, arrives in the province. The Spanish Squadron pays a surprise visit to Monterey. After departing, the three ships cross the Pacific. The crew mutinies at Guam and returns to Monterey where they surrender to Mexican authorities. |
| 1826 | Trapper Jedediah Smith visits California. |
| 1828 | Mexican provincial governors are authorized to give land grants to contractors, families, and individuals. |
| 1829 | Revolt at Mission Santa Clara. After two failed expeditions against Estanislao's racheria, a corps of Californios and Indians from Monterey massacres the renegades. Joaquin Solís leads unpaid soldiers at the Monterey presidio in revolt. Solís is aided by Jose María Herrera, who has been plotting since 1827. Mexico abolishes slavery. |
| 1830 | Solís flees the Battle of La Cienequita after loyal Californios from Santa Barbara return his fire. Monterey citizens retake their presidio. Governor Jose María Encheadia orders secularization of the Missions. |
| 1831 | New Governor Don Manuel Victoria countermands the secularization order issued by his predecessor. |
| 1834 | Secularization of Mission properties begins. Gold is discovered on Catalina Island. J.B.R. Cooper builds a sawmill on the Russian River. Augustin Zamorano publishes the first books issed in California. |
| 1835 | General Mariano Vallejo grants three Yankee sailors considerable land near Bodega Bay as a check against Russian expansion. Los Angeles becomes a city. The San Diego presidio is abandoned. Foundation of Sonoma Pueblo. United States offers to buy California from Mexico. |
| 1836 | The provincial legislature declares California independent from Mexico. President Anastasio Bustamante defuses the situation by appointing Juan B. Alvarado and Don Carlos Carrillo, both liked by Californios, as governors. Father Mercado protests against cruel treatment of Indians by San Antonio Mission operator J.M. Ramirez. |
| 1839 | Citizens complain about the increase in Indian-related crime following the secularization of the missions. |
| 1840 | First California Supreme Court, Tribunal de Justicia, created. John Sutter acquires 11 square leagues of land around the present city of Sacramento, a holding he calls New Helvetica after his native Switzerland. Two Years Before the Mast by Richard Henry Dana. The anonymous publication of this book excites the American imagination about the possibilities of California. |
| 1841 | Wilkes Expedition arrives in San Francisco. James A. Dana reports that he has found gold in the American River. Abel Stearns and Alfred Robinson send 20 ounces of gold to the Philadelphia Mint, the first such shipment from Alta California. John Sutter buys Fort Ross from the Russians. Bidwell/Bartleson Party crosses the continent, marking the arrival of the first organized group of settlers from the United States. |
| 1842 | Discovery of gold in Placerita Canyon by Francisco Lopez, a shepherd. Manuel Micheltorena is sent from Mexico to serve as governor of the Alta California province. He proves unpopular. Thomas ap Catsby Jones sails in Monterey Bay and demands the presidio's immediate surrender after hearing in Peru that the United States and Mexico are at war. The U.S. Consul assures him that this is not the case. Jones apologizes to the provincial governor and leaves. |
| 1843 | Governor Micheltorena attempts to "renanimate the skeleton of the giant" by reopening twelve of the Franciscan Missions. The Indian owners of Pueblita de Las Flores cede their lands to the Pico brothers. Thomas O. Larkin becomes the only United States consul to serve in Monterey. |
| 1844 | John C. Fremont arrives in California as part of an Army Topographical Expedition. He discovers Lake Tahoe enroute. First overland wagon train via the Truckee/Donner Pass route. |
| 1845 | Mexican Government forbids further American emigration to California. Americans who are not married to California women are asked to leave. William Gulnac sells his "El Camp de los Francesces (French Camp) to Charles M. Weber for $60. Discovery of Big Bear Valley by Benjarmin Wilson. |
| 1846 | The United States declares war on Mexico. (May 13) American settlers, panicked by reports of a Californio raiding party, capture Sonoma and raise the Bear Flag as they declare independence from Mexico. (June 14) Applegate Cutoff established. Commodore John Sloat captures Monterey, marking the end of the provincial governorship. (July 7) The Stars and Stripes are raised in Yerba Buena (San Francisco). (July 9) The Brooklyn, bearing Sam Brannan and other Mormon settlers bound for Zion, arrives in San Francisco. (July 31) The Californian, a newspaper written in both English and Spanish, is published in Monterey. (August 15) Juan Flaco Brown rides from Los Angeles to San Francisco, bearing the news to Commodore Stockton that the American detachment at Los Angeles is under siege. When his horse fails him, he walks the last twenty seven miles of the five hundred mile journey. (September 24 to 28) Battle of Chino Rancho. Captain José María Flores leads a rebellion against the American garrison at Los Angeles. The Americans are routed in their first encounter. Heavy snows trap members of the Donner Party in the High Sierra. The Battle of San Pasqual ends in an embarassing defeat for weary American cavalry led by General Stephen Kearny. (December 5) Pauma Massacre. Luisenño Indians ambush Californio survivors of the Battle of San Pasqual near Mission San Luis Rey. Eleven Californios die.(December) |
| 1847 | The Battle of Santa Clara. U.S. forces defeat the last Californio resistance in northern California. (January 2). Battle of San Gabriel. The United States forces under naval Commodore Robert Stockton defeats Flores troops. Capitulation of Cahuenga. (January 13) Stockton appoints Army Captain John C. Fremont as first American Governor of California. (January 19) Arrival of Mormon Battalion at Los Angeles. E. Clampus Vitus organized in Pennsylvania. General Phillip Kearny removes Fremont as Governor of California. (March 1) The last surviving member of the Donner Party is rescued. There have been five rescue missions. 41 people out of 87 original party members have died. Fremont is arrested at Fort Leavenworth, Kansas, charged with insubordination, court-martialed, and sentenced to dismissal. After his pardon by President Polk, he declines clemency and resigns from the Army. First brick house in the state built at Sutterville. California Star newspaper established in San Francisco by Sam Brannan. Charles A. Weber founds the settlement of Tuleburg. It will soon become the City of Stockton. |
| 1848 | James Marshall discovers gold in the American River. Treaty of Guadalupe Hildago ends the Mexican-American War. California becomes a territory of the United States. |