The road was bypassed by the three-lane Ridge Route Alternate, then U.S. Route 99 (US 99), to handle increased traffic and remove curves; the Alternate in Los Angeles County was completed in 1933, and Kern County line to Grapevine in 1936. The four-lane US 99 was completed in 1953 and replaced by an eight-lane freeway, Interstate 5 (I-5) in 1960-70. The portion of the road in the Angeles National Forest was added to the National Register of Historic Places in 1997, by the efforts of Harrison Scott. Much of the road has been closed by the U.S. Forest Service; other remnants are used by local traffic.