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 . Then U.S. 101 takes an inland route through the Salinas Valley , while Highway 1 heads northwest , running along the Pacific coastline in California , parallel and to the west of U.S. 101 .