For those not familiar, the Ridge Route was realigned quite a bit in the mid-1920's. In the process, many sections of wooden railing and concrete curbing were lost. Still, the road did need it. One of the more "famous" realignments was known as the "Callahan Line Change" where multiple reversing curves were replaced in a somewhat dramatic fashion with one long curve. As it happens, this section was yet again realigned when I-5 was built, almost completely obliterating any trace of it. Almost, that is.
https://socalregion.com/highways/ridge_route/rrt003/