The first recorded structural fire in Orange County is accidentally ignited by a boy who overturns a candle in a Mission San Juan Capistrano storeroom.

The first New England frigate Alexander anchors off Capistrano Bay seeking food and water. Their stopover is tolerated but not welcomed.

After nine years under construction, the new stone church at the Mission San Juan Capistrano is dedicated with the governor and president of missions in attendance.

The Russian-flagged vessel Mercury lands off the OC coast to disgorge a gang of Alaskan otter hunters. The Los Angeles pueblo dispatches a government officer to demand the ship’s departure, but not before the crew is able to load 2,000 otter pelts into its hold.

Sergeant Jose Antonio Yorba and Juan Pablo Peralta receive grazing rights to more than 62,000 acres centered upon Santiago Creek from Santa Ana Canyon to Newport Beach. It is the first land grant entirely within OC. The Yorba adobes also form the first permanent settlement in OC outside of San Juan Capistrano. OC suffers its first recorded flood.

An earthquake collapses church walls at the Mission San Juan Capistrano, killing 40 people (including the two unfortunate young bell-ringers) and causing serious damage. The mission claims to have 1,400 residents providing 500,000 pounds of wheat, 190,000 pounds of barley, 202,000 pounds of corn, 20,600 pounds of beans, 14,000 cattle, 16,000 sheep and 740 horses. A flock of cliff swallows begin to build nests in the only wall of the church that survived the earthquake.

While Argentina is in revolt against Spain, Argentine pirate Hippolyte Bouchard raids the California coastline from his vessels Argentina and Santa Rosa. A landing party from his ship approaches the Mission San Juan Capistrano under a truce flag hoping to obtain supplies. The military garrison at the mission threatens to fire upon the party. Bouchard angrily dispatches a larger party of 140 men to loot the nearby town. The military garrison offers a lackluster defense. The mission priests evacuate to the Trabuco Hills with mission valuables, leading to stories of buried treasure.

Mexico wins independence from Spain. Residents in OC don’t receive word until the following year.

The Mexican flag rises over OC, replacing the flag of Spain.

Diego Sepulveda’s Adobe Estancia is built as a stopover between the Missions San Juan Capistrano and San Gabriel.

The Balboa peninsula is formed by a Santa Ana River flood.

Smallpox breaks out at San Juan Capistrano. Fur trapper James Ohio Pattie, imprisoned by Mexican authorities as an illegal immigrant (and suspected spy for Spain), is released because he knows how to administer vaccinations to the outbreak. He vaccinates 600 people at San Juan Capistrano.

A small band of Indians are massacred in Black Star Canyon.

The Mexican government orders that California’s missions are secularized and taken from the control of the church. Although the lands are to be divided among the Indian residents, Mexican rancheros manage to acquire the lands for themselves.

Bernardo Yorba is granted Rancho Cañon de Santa Ana (future Yorba Linda). Juan José Nieto is granted Rancho Los Alamitos (future Los Alamitos, Seal Beach, Cypress, Stanton, Fountain Valley and Westminster). Both land grants were originally part of Rancho Las Bolsas.

The Boston trading ship Pilgrim with writer Richard Henry Dana aboard (Two Years Before the Mast) visits the OC coast.

Juan Pacifico Ontiveras is granted Rancho San Juan Cajon de Santa Ana (future Anaheim, Fullerton, Brea and Placentia). Jose Sepulveda is granted Rancho San Joaquin (future Irvine, Tustin and Newport Beach).

Mariano R. Roldan is granted Rancho La Habra (future La Habra).

Capistrano is designated a Mexican pueblo or township rather than a religious parish. It is temporarily renamed San Juan de Arguello after a former unpopular administrator, Santiago Arguello. Arguello was despised for nepotism and allowing the Argentine pirates to loot and humiliate the town. For his trouble, Arguello is granted Rancho Trabuco (future Mission Viejo and Rancho Santa Margarita). Jose Antonio Estudillo is granted Rancho La Paz (future Rancho Mission Viejo). Joaquín Ruiz is granted Rancho Bolsa Chica (future Huntington Beach) after its separation from Rancho Las Bolsas.

A visiting French diplomat, Count Eugene Duflot de Mofras describes San Juan Capistrano as "an establishment which is in a most ruinous condition, despite the efforts made by its Spanish missionary, Father José Maria Zalvidea, to arrest the destruction." Jose Serrano is granted Rancho Canada de los Alisos (future Lake Forest) and Juan Avila is granted Rancho Niguel (future Laguna Niguel).

Englishman Juan (John) Forster and husband of Mexican Governor Pio Pico’s sister Ysidora, acquires the Rancho Trabuco (future Mission Viejo and Rancho Santa Margarita) from Santiago Arguello.

Augustin Olvera, the Los Angeles judge and close friend to (and after whom the future Olvera Street in Los Angeles would be named), acquires Rancho Mission Viejo (formerly Rancho La Paz).

Just two days after Augustin Olvera takes final title to Rancho Mission Viejo, rancher Juan Forster (formerly John Forster), acquires the rancho. Forster also offers the highest bid of $710 for the property of Mission San Juan Capistrano and makes his home in the mission.

In the waning days of Mexican California, Emigdio Vejar is granted Rancho Boca de la Playa (future Dana Point, San Clemente and southern San Juan Capistrano) and Teodocio Yorba is granted Rancho Lomas de Santiago (future part of Irvine Ranch). Mexican Governor Pio Pico flees California ahead of invading American forces after taking refuge in Santiago Canyon and on Trabuco Mesa. Additional American forces under the command of Major John C. Fremont march through OC towards Los Angeles.

Rancher Juan (John) Forster provides fresh horses to American military forces led by Commodore Robert F. Stockton and General Kearney on their march from San Diego to retake Los Angeles. The force camps in Lake Forest then in Olive along the way.