Santa Paula is a city in Ventura County, California, United States. Situated amidst the orchards of the fertile Santa Clara River Valley, the city advertises itself to tourists as the "Citrus Capital of the World." Santa Paula was one of the early centers of California's petroleum industry. The Union Oil Company Building, the founding headquarters of the Union Oil Company of California in 1890, now houses the California Oil Museum. The population was 29,321 at the 2010 census, up from 28,598 at the 2000 census.