In this overview of the hills in the northern portion of Los Angeles County can be seen the building and carving out of the original Ridge Route. It was built between 1913 and 1915. The road ran from Castaic to Gorman and opened a path to the San Joaquin Valley via Tejon Pass on the northern end. It was replaced in 1933 by an Alternate Ridge Route which was shorter, and even later by Interstate 5 (Golden State Freeway).