The first orange grove in California is planted at the Mission San Gabriel. California is divided into Alta California and Baja California.
The first American to visit Los Angeles is Captain Jose Shaler, captain of the Lelia Byrd, returning to New England from the Hawaiian Islands.
Padres from the San Fernando Mission dam the waters of the Los Angeles River north of El Pueblo, provoking a confrontation in court. The court rules in favor of El Pueblo. An Indian revolt erupts at the Mission San Gabriel.
Severe flooding occurs.
The Ayuntamiento (city council) is established.
The Plaza Church cornerstone is laid.
Torrential rains flood out El Pueblo, forcing it to relocate to higher ground. The Los Angeles River changes its outlet to the sea from San Pedro to the Ballona wetlands. A Russian trader, Boris Tarakanaf, is the first foreigner jailed in El Pueblo. José Antonio Rocha, born in Portugal, becomes the first foreigner to settle in El Pueblo.
The first school is established, headed by Maximo Pina, a retired soldier. It fails after two years.
American Joseph Chapman is shipwrecked at San Pedro and arrested as a pirate. After a brief jail term, he chooses to stay in El Pueblo and becomes an active member of the community. He becomes the first American and English-speaking person to settle in Los Angeles. After repeated floods, El Pueblo moves to a higher location. The Avila Adobe is built.
A year after Mexico frees itself from Spanish rule, El Pueblo learns of the revolution and swears allegiance to the new independent nation. The Plaza Catholic Church is completed.
The Los Angeles River changes its outlet back from the Ballona wetlands to San Pedro.
A party of American trappers led by Jebediah S. Smith arrives in El Pueblo from the Salt Lake Valley in Utah. They are the first Americans to arrive in California overland. They are ordered to leave by the authorities, but Smith later returns. The first priest permanently assigned to Los Angeles arrives.
John Temple opens El Pueblo’s first general store.
John Groningen, a new resident in El Pueblo, purchases the local Yang-Na Indian village and expels its residents. The site later becomes the Los Angeles Civic Center.
Governor José Maria Echeandia issues a proclamation to secularize all California missions. A month later, the new governor, Manuel Victoria, annuls the proclamation that leads to the arrest and banishment of several prominent citizens of El Pueblo. A brief, local war erupts, forcing Governor Victoria out of California and re-establishing the original plan to secularize the missions. California is divided into northern and southern provinces. Pio Pico becomes governor of the southern province and establishes his government in Los Angeles.
Heaving flooding occurs.
The Mexican Congress passes the Secularization Act that places the Mission San Gabriel and the Mission San Fernando under civil management.
The dismantling of the missions begins. Mission padres order the slaughter of over 100,000 cattle at the Mission San Gabriel in response to the impending takeover.
Los Angeles is given the status of a "city" by the Mexican Congress replacing Monterey as capital of California. Richard Henry Dana’s voyage aboard the Pilgrim brings him to the Los Angeles area. His descriptions of California in his book Two Years Before the Mast sparks interest in California. The second largest ethnic group in the city is French.
A local civil war breaks out between northern and southern California. Indian forced labor is initiated. The Mexican government takes the first official census of Los Angeles. The population is fixed at 2,228. This includes 603 men, 421 women, 651 children and 553 "domesticated Indians." Among Los Angeles residents are 29 Americans, 4 Britons, 3 Portuguese, 2 Africans, and a Canadian, Irishman, Italian, German, Scot, Norwegian, and Curacao. The first vigilante committee forms in Los Angeles to seize a man and woman from the authorities accused of murdering the woman's husband. The pair are executed by the "committee."
Governor Alvarado exiles all foreigners who would not become Mexican citizens. The first multi-story home is built on the Plaza.
One of the first California-bound wagon trains, the Workman-Rowland party, arrives in Los Angeles from New Mexico. William Wolfskill plants the first commercial orange grove in California. Oranges had otherwise been grown in the area since 1804.
Francisco Lopez makes California’s first gold discovery in Placerita Canyon in the Santa Clarita Valley.
The local California civil war ends with the battle of Cahuenga Pass. The casualties are one horse and one mule. Pio Pico is made governor of all of California and Los Angeles is finally recognized as the provincial capital. Rancho Encino is established.
The United States declares war on Mexico. U.S. Navy Commodore Robert F. Stockton lands his forces at San Pedro (August 6) and, finding Mexican government leaders had fled, encounter no resistance as they enter the Pueblo of Los Angeles (August 13). The U.S. flag is raised for the first time over Los Angeles. A small unit of U.S. marines are left to garrison Los Angeles. Later, having endured petty bullying by the U.S. Marines left in Los Angeles, local residents revolt and force the Americans to surrender. The Americans are allowed to withdraw without harassment to San Pedro with the understanding that they depart the area. Stockton responds by sending 200 U.S. reinforcements to San Pedro, commanded by U.S. Navy Captain William Mervine, to meet the marines. After a poorly-executed attack on the defending Californios in the "Battle of the Old Woman's Gun" at Rancho San Pedro (modern Rancho Dominguez), the U.S. force is again forced to withdraw and evacuate from San Pedro. They leave behind four men buried at San Pedro who had died from wounds sustained in the fighting.
U.S. forces engage and defeat Mexican defenders at the Battle of the San Gabriel River and proceed to recapture Los Angeles (January 10). Mexican military commander Andrés Pico, on behalf of the Californios, capitulate to the Americans after negotiating the Treaty of the Cahuenga Ranch near Los Angeles (January 13). Fort Moors is dedicated by the U.S. Army in Los Angeles as part of the city’s first celebration of American Independence Day.