State Route 33 (SR 33) is a north–south state highway in the U.S. state of California. It runs north from U.S. Route 101 in Ventura through the Transverse Ranges and the western side of the San Joaquin Valley to Interstate 5 at a point east of Tracy. SR 33 replaced part of U.S. Route 399 in 1964 during the "great renumbering" of routes. In the unincorporated sections of Kern County it is known as the West Side Highway. In addition, the California Legislature designated the entire Kern County portion as the Petroleum Highway in 2004. The southernmost portion in Ventura is a freeway known as the Ojai Freeway, while it is known as the Maricopa Highway from Ojai to Maricopa.