Ventura County (/vɛnˈtʊərə/) is a county located in the southern part of the U.S. state of California. The largest city is Oxnard,
 and the county seat is the city of Ventura.

 In October 1542, the expedition led by Juan Rodríguez Cabrillo anchored in an inlet near Point Mugu; its members were the
 first Europeans to arrive in the area that would become Ventura County.

 Active occupation of California by Spain began in 1769. Gaspar de Portolà led a military expedition by land from San Diego
 to Monterey, passing through Ventura County in August of that year. A priest with the expedition, Father Juan Crespí, kept a
 journal of the trip and noted that the area was ideal for a mission to be established and it was a "good site to which nothing is
 lacking". Also on this expedition was Father Junípero Serra, who later founded a mission on this site.

 On March 31, 1782, the Mission San Buenaventura was founded by Father Serra. It is named after Saint Bonaventure, one of
 the early intellectual founders of the Franciscan order. The town that grew up around the mission was originally named San
 Buenaventura (and retains the name officially), it has been known as Ventura since 1891.

 In the 1790s, the Spanish Governor of California began granting land concessions to Spanish Californians who were often
 retiring soldiers. These concessions were known as ranchos and consisted of thousands of acres of land that were used
 primarily as ranch land for livestock. In Ventura County, Rancho Simi was granted in 1795 and Rancho El Conejo in 1802.
 Fernando Tico was granted Ojai and part of Ventura by Gov. Alvarado.

 The Mexican–American War began in 1846 but its effect was not felt in Ventura County until 1847. In January of that year,
 Captain John C. Frémont led the California Battalion into San Buenaventura to find that the Europeans had fled, leaving only
 the Indians in the Mission. Fremont and the Battalion continued south to sign the Treaty of Cahuenga with General Andrés
 Pico. The Treaty of Guadalupe Hidalgo formally transferred California to the United States in 1848.

 By 1849, a constitution had been adopted for the California territory. The new Legislature met and divided the pending state
 into 27 counties. At the time, the area that would become Ventura County was the southern part of Santa Barbara County.

 The 1860s brought many changes to the area. A drought caused many of the ranchos to experience financial difficulties and
 most were divided, sub-divided and sold. Large sections of land were bought by eastern capitalists based on favorable reports
 of petroleum deposits. A United States Post Office was opened at Mission San Buenaventura in 1861. On April 1, 1866, the
 town of San Buenaventura was incorporated, becoming the first officially recognized town in what would become Ventura
 County.

 On January 1, 1873, Ventura County was officially split from Santa Barbara County, bringing a flurry of change. That same
 year, a courthouse and wharf were built in San Buenaventura. A bank was opened and the first public library was created. The
 school system grew, with the first high school opening in 1890.