Ventura (officially the City of San Buenaventura; commonly called San Buenaventura before 1891) is the county seat of Ventura County, California, United States, incorporated in 1866. The population was 106,433 at the 2010 census, up from 100,916 at the 2000 census. Ventura is accessible via U.S. Route 101, State Route 33, and State Route 126.
Father Junípero Serra founded Mission San Buenaventura in 1782, forming the basis of what would become the city. The mission was named for St. Bonaventure, a Thirteenth Century Franciscan saint and a Doctor of the Church. The first mission burned in 1801 and a replacement building of brick and stone was completed in 1809. The bell tower and facade of the new mission was destroyed by an 1812 earthquake. On July 6, 1841, Governor Juan Bautista Alvarado granted Rancho San Miguel to Felipe Lorenzana and Raymundo Olivas, whose Olivas Adobe on the banks of the Santa Clara River was the most magnificent hacienda south of Monterey.
The inhabitants at the time of the arrival of the Spanish in the late 18th Century were a local band of the Chumash tribe (the Mitskanaka). Archaeological research demonstrates that the Chumash have deep roots in central and southern coastal regions of California, and lived here for millennia. 
After the American Civil War, settlers came to the area, buying land from the Mexicans, or simply as squatters. Vast holdings were later acquired by Easterners, including the railroad magnate, Thomas Scott. He was impressed by one of the young employees, Thomas R. Bard, who had been in charge of train supplies to Union troops, and Bard was sent west to handle Scott's property.
Not easily accessible, Ventura was not a target of immigrants, and as such, remained quiet and rural. For most of the century which followed the incorporation of Ventura in 1866, it remained isolated from the rest of the state.
Bard is often regarded as the Father of Ventura and his descendants have been prominently identified with the growth of Ventura County. The Union Oil Company was organized with Bard as President in 1890, and has offices in Santa Paula. The large Ventura Oil Field was first drilled in 1919 and at its peak produced . The city is located between the Ventura River and the Santa Clara River, leading to soil so fertile that citrus grew better here than anywhere else in the state. The citrus farmers formed Sunkist Growers, Incorporated, the world's largest organization of citrus production.
On March 12, 1928, the St. Francis Dam, 54 miles (87 km) inland, failed catastrophically, taking over 600 lives. The resulting flood reached Montalvo about 5:30 a.m., almost two miles (3 km) wide and traveling at a speed of 5 miles (8 km) per hour.
From the south, travel by auto was slow and hazardous, until the completion of a four-lane freeway (US Highway 101) over the Conejo Grade in 1959. This route, now further widened and improved by 1969, is known as the Ventura Freeway, which directly links Ventura with the Los Angeles metropolitan area. Another route, US Highway 101 ALT (now the Pacific Coast Highway) traveled along the coast from Santa Monica via Oxnard, but was not heavily used.
From the north, entrance was by way of a single road along the beach and stagecoach passengers either had to wait until low tide when the horses could cross on the exposed wet sand, or go up the Ventura River Valley and then cross over the mountains to Santa Barbara via Casitas Pass, a long and difficult trip.
Inland, Ventura was hemmed in by (what is now) the Los Padres National Forest, composed of mountainous country and deep canyons. This route became passable with the completion of the Maricopa Highway (Hwy 33) in the 1930s.
Since then, Ventura has grown steadily. In 1920 there were 4,156 people. In 1930 the population had increased to 11,603, by 1950 the population reached 16,643, by 1970 the population was 57,964, and in 1980 the population had increased to 73,774. In the last three decades it has increased to approximately 107,000.