U.S. Route 101

U.S. Route 101, or U.S. Highway 101 (US 101), is a major north–south highway that traverses the states of California, Oregon, and Washington on the West Coast of the United States. It is part of the United States Numbered Highway System and runs for over 1,500 miles (2,400 km) along the Pacific Ocean. The highway is also known by various names, including El Camino Real in parts of California, the Oregon Coast Highway, and the Olympic Highway in Washington. Despite its three-digit number, normally used for spur routes, US 101 is classified as a primary route with 10 as its "first digit".

The highway's southern terminus is at a major interchange with Interstate 5 (I-5) and I-10 in Los Angeles. US 101 follows several freeways in Southern California as it travels north of the Santa Monica Mountains and along the coast, where it is concurrent with California State Route 1 (SR 1). The highway travels inland from the coast after it splits from SR 1 and approaches the San Francisco Bay Area, where it becomes the Bayshore Freeway and later traverses San Francisco on city streets to reach the Golden Gate Bridge. US 101 continues north on the Redwood Highway and rejoins the coast before it enters Oregon.

The Oregon Coast Highway carries US 101 through the state's coastal towns and regions in the foothills of the Oregon Coast Range. The highway crosses over the Columbia River on the Astoria–Megler Bridge into Washington, where it follows Willapa Bay and an inland route to Aberdeen and Olympic National Park. US 101 travels north and east around the Olympic Peninsula and reaches its northernmost point in Port Angeles; from there, it travels east and later south to its northern terminus at I-5 in Tumwater, near Olympia. Several portions of the highway are also designated as scenic byways, including the Pacific Coast Scenic Byway in Washington; US 101 also serves three national parks: Pinnacles, Redwood, and Olympic.

The highway is a major north–south link along the Pacific coast north of San Francisco but does not serve the largest cities in Oregon and Washington; that role is instead filled by I-5, which has a more direct inland routing. US 101 was established in 1926 and followed several historic routes, including El Camino Real, which linked California's early Spanish missions, pueblos, and presidios. It originally terminated to the south in San Diego but was truncated to Los Angeles in 1964 after the construction of I-5. Other sections were later moved to freeway alignments that bypassed cities. Several sections of US 101 in Washington and Oregon were rebuilt in the mid-20th century to eliminate curves and address traffic congestion. Later projects expanded the Bayshore Freeway in the San Francisco Bay Area and relocated sections of the highway in Oregon in response to landslides and erosion.

US 101 is a major highway that generally follows the Pacific Ocean through the West Coast states of California, Oregon, and Washington. It spans over 1,500 miles (2,400 km) from its southern terminus in Los Angeles to its northern terminus near Olympia, Washington. US 101 generally runs parallel to I-5, which serves most of the West Coast's largest cities and is designated for long-haul freight. The corridor is also designated as part of U.S. Bicycle Route 95 (USBR 95) in Northern California and is proposed to be part of USBR 40 and USBR 97 in Washington.

The highway is known by several names that vary between the states. In California, portions of US 101 are part of the Santa Ana Freeway, Hollywood Freeway, Ventura Freeway, Bayshore Freeway, and Redwood Highway. In Oregon, it is officially the Oregon Coast Highway No. 9 under the named highways system and part of the Pacific Coast Scenic Byway, a National Scenic Byway. In Washington, it is officially part of the Pacific Coast Scenic Byway, a state scenic highway. In Southern California, US 101 is commonly called "the 101" (pronounced "the one oh one").

US 101 travels on several major freeways in the Greater Los Angeles area, including some of the most congested roads in the United States. Its southern terminus is in Boyle Heights at the 135-acre (55 ha) East Los Angeles Interchange, one of the busiest freeway junctions in the United States, where US 101 meets I-5, I-10, and SR 60. The highway travels north on a section of the Santa Ana Freeway and turns west to cross the Los Angeles River after merging with the San Bernardino Freeway. The Santa Ana Freeway continues across Downtown Los Angeles and passes Union Station, a major transit hub, and government buildings before it reaches a junction with SR 110. Beyond Downtown Los Angeles, US 101 uses the Hollywood Freeway as it travels northwest through the eponymous neighborhood towards Cahuenga Pass, where it crosses the Hollywood Hills and passes Universal Studios Hollywood. The highway leaves the Hollywood Freeway to turn west onto the Ventura Freeway, which travels along the southern edge of the suburban San Fernando Valley and intersects I-405. US 101 continues into Ventura County, where it joins SR 1 and serves communities in the Conejo Valley and Oxnard Plain.

The highway follows the Pacific Ocean northwest from Ventura through Santa Barbara, where it separates the downtown from its beach, and Goleta. US 101 becomes a divided highway beyond Goleta as it turns north at Gaviota State Park to cross the Santa Ynez Mountains at Gaviota Pass; SR 1 splits to remain closer to the coastline, as it does in several areas of the state. The highway continues inland and travels around the Purisima Hills to reach Santa Maria, where the freeway resumes as it bypasses the city. US 101 briefly returns to the coastline near Pismo Beach and turns inland over the Irish Hills towards San Luis Obispo alongside SR 1. The highway crosses the Santa Lucia Range through Cuesta Pass and follows the Salinas River northwest through Atascadero and the wine-growing region surrounding Paso Robles. US 101 passes near Pinnacles National Park and travels through the city of Salinas, where it turns northeast to cross the Gabilan Range. From there, the highway descends into the Santa Clara Valley and Gilroy, the southernmost city in the San Francisco Bay Area.