The Ridge Route refers to the section of highway between Castaic and Grapevine, through the Tejon Pass. The highway had its origins in the early 1910s, when a route was needed to connect Los Angeles to the Central Valley. Some believed that the only option was the route through Mojave and the Tehachapi Mountains, but a new route was discovered through the Tejon Pass. This route became known as the Ridge Route and saw almost constant planning, construction, and improvement from 1914 to 1970.