In the U.S. state of California, U.S. Route 101 (US 101) is one of the last remaining and longest U.S. Routes still active in the state, and the longest highway of any kind in California. US 101 was also one of the original U.S. Routes established in 1926.
Although the highway has been superseded in overall importance for transport through the state by Interstate 5, US 101 continues to be the major coastal north–south route that links the Greater Los Angeles Area, the Central Coast, the San Francisco Bay Area, and the North Coast (Redwood Empire). Significant portions of US 101 between the Los Angeles area and the San Francisco Bay Area follow El Camino Real, the historic road connecting the former Alta California's 21 missions. US 101 also has portions designated as the Santa Ana Freeway, Hollywood Freeway, Ventura Freeway, South Valley Freeway, and the Bayshore Freeway. The Redwood Highway, the 350-mile-long (560 km) northernmost segment of the highway, begins at the Golden Gate and passes through the world's tallest and only extensive preserves of virgin, old-growth coast redwood trees.