California State Route 1 in western San Mateo County traverses the Montara Mountain spur of the Santa Cruz Mountains. In modern times California State Route 1 passes through Montara Mountain via the Tom Lantos Tunnels and the highway is traditionally associated with Devils Slide. Although Devils Slide carries an infamous legacy due it being prone landslides it pales in comparison to the alignment California State Route 1 carried prior to November 1937 over Old Pedro Mountain Road.
Old Pedro Mountain Road opened to traffic in 1915 and is considered one of the first major asphalted highways in California. Old Pedro Mountain Road clambers over a grade from Montara towards Pacifica via the 922-foot-high Saddle Pass. Pictured above an overlook of Old Pedro Mountain Road facing southward towards Montara as it appears today. Pictured below it the same view during June 1937 when it was part of the original alignment of California State Route 1. Today Old Pedro Mountain Road sits abandoned and eroding away as part of a trail within Montara State Beach.
- Originally published July 25, 2021.
- Updated July 22, 2022.
Part 1; the history of Old Pedro Mountain Road
Prior to Old Pedro Mountain Road travel over Montara Mountain (sometimes referred to as San Pedro Mountain) was difficult. Prior to the arrival of Europeans, a well-established Native American overland trail existed over Montara Mountain.
Originally overland travel south of San Francisco towards the Montara Mountain Trail followed the shoreline beaches towards Mussel Rock. During 1874 and early 1875 a highway tunnel was built through Mussel Rock at the behest of Hibernia Bank co-founder Richard Tobin. Tobin desired to be able to travel via stagecoach from his home at Rockaway Beach near the Montara Mountain Trail north to his family's homestead in San Francisco.
The Mussel Rock Tunnel was possibly the first highway tunnel in California, but ultimately proved to be impractical. The Mussel Rock Tunnel was infamous for filling with sand during high tides and never properly functioned as a through highway. The Mussel Rock Tunnel was claimed to be 90 feet in length and was excavated largely via explosives. Ultimately the much of the Mussell Rock Tunnel and approach roads were destroyed during the 1906 San Francisco Earthquake. The Mussell Rock Tunnel is sometimes referred to as "Tobin's Folly."
The May/June 1956 California Highways & Public Works featured the Mussel Rock Tunnel. At the time much of the history of the Mussel Rock Tunnel was unclear and it was thought to have been constructed during the 1830s as part of Mexican Rancho San Pedro. A more accurate history of the Mussel Rock Tunnel can be found in the 2010 San Francisco State University document titled Living on the edge: History at Mussel Rock, Daly City, California.
The Mussel Rock Tunnel and Montara Mountain Trail were replaced in 1879 when San Mateo County completed the Half Moon Bay-Colma Road. The Half Moon Bay-Colma Road was built largely west of Old San Pedro Mountain Road above the modern Tom Lantos Tunnels. The general path of the Half Moon Bay-Colma Road can be seen traversing Montara Mountain on the 1882 Bancroft's Map of California and Nevada.
During the early 20th Century, the Half Moon Bay-Colma Road reportedly was incredibly difficult for early automobiles to traverse as it was extremely narrow and featured grades as high as 25%. The Half Moon Bay-Colma Road can be seen in greater detail between Montara north towards Rockaway Beach (now in Pacifica) on the 1914 C. F. Weber & Company Map of San Mateo County.
CA 1/LRN 56 can be seen traversing Old Pedro Mountain Road on the 1935 Division of Highways Map of San Mateo County. CA 1/LRN 56 can be seen approaching Old Pedro Mountain Road through Farallone City and Montara via; Farallone Boulevard, 4th Street, Audubon Avenue, George Street and Elm Street. CA 1/LRN 56 can be seen entering Rockaway Beach on what is now Higgins Way.
The final climb to Saddle Pass winds through the overgrown on Old Pedro Mountain Road to a trail marker with directions to Montara and Pacifica.