High Quality Content by WIKIPEDIA articles! The Ridge Route, officially the Castaic-Tejon Route, was a two-lane highway running between Los Angeles and Kern counties, California. Opened in 1915 and paved with concrete between 1917 and 1921, the road was the first paved highway directly linking the Los Angeles Basin with the San Joaquin Valley over the Tejon Pass and the rugged ridge south of Gorman. Most of the road was bypassed in 1933 by the Ridge Route Alternate (then U.S. Route 99), which has since been upgraded to a modern freeway, Interstate 5.