The precursor to the Santa Ana Freeway between Los Angeles and Anaheim was U.S. Route 101 Bypass from the early 1940s to the mid-1950s, when it became part of US 101. Old US 101 there is now partially SR 72.
US 101 Business in Ventura, California is a business loop that follows the former U.S. 101 alignment before the construction of the Ventura Freeway. The route runs along the entirety of Thompson Boulevard and portions of Main Street and Garden Street.
US 101 Business, called Wildwood Avenue, is a business loop of US 101 through Rio Dell. Its southernmost section between US 101 near Scotia to the north end of the Eel River Bridge is legally defined as an unsigned California State Route 283.
U.S. Route 101 Business is a business loop of US 101 that travels from Astoria to Warrenton. It is a former alignment of US 101, bypassed in 1964 when a new bridge opened across Youngs Bay. It was originally designated U.S. Route 101 Alternate until about 1976.
Major intersections
The entire route is in Clatsop County.