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California State Route 1 Tom Lantos Tunnels/Old California State Route 1 Devil's Slide


No weekend in the Bay Area is really complete in my opinion without a good hike.  That being the case after completing Interstate 380 and driving part of California State Route 82 on the historic alignment of US 101 I made my way south along the coast on CA 1 towards Half Moon Bay.  My destination was the Devil's Slide Trailhead just south of the Tom Lantos Tunnels.

The Devil's Slide is the second alignment of CA 1 between Pacifica and Montara in San Mateo County while the Tom Lantos Tunnels are the third alignment.  .The original alignment of CA 1 in 1934 prior to the Devil's Slide between Pacifica and Montara was over Pedro Mountain Road.  Pedro Mountain Road alignment was adopted into Legislative Route Number 56 by 1933 according to CAhighways.org.  The alignment over Pedro Mountain Road and Higgins Way are very apparent on the 1935 California Division of Highways Map of San Mateo County. 

1935 California Divisions of Highway Map of San Mateo County

The Devil's Slide refers to a promontory region between Pacifica and Half Moon Bay which is part of the Montara Mountain sub-range of the Santa Cruz Mountains.  Devil's Slide in particular has natural slopes approaching 50% in places which makes the area particularly landslide prone.  Most historic transportation access prior to the 20th Century sought to avoid Devil's Slide and it wasn't until 1905 when the Ocean Shore Railway started building a line through area.  The 1906 San Francisco Earthquake destroyed much of the tracks laid at Devil's Slide but the Ocean Shore Railway eventually opened in 1908.  The goal of the Ocean Shore Railway was to create a 73 mile line between San Francisco and Santa Cruz but the northern segment never made it past Half Moon Bay before it shuttered in 1920.

In 1935 construction of a new alignment of CA 1 began at Devil's Slide and was completed by late 1937.  The Devil's Slide section of CA 1 was one of the historically most infamous along the entire highway with the first major closure coming in 1940 due to a rock slide.  The Devil's Slide area of CA 1 closed due to slides for 2 years in 1995 and had a 6 month closure in 2006 due to an eroding road deck.  Eventually CA 1 was realigned through the Tom Lantos Tunnels which were under construction from 2005 to 2013.  Both tunnels are about 4,000 in length and carry on direction of highway travel.

In 2014 the former grade of CA 1 was converted to the 1.3 mile Devil's Slide Trail which has dual trailheads at both ends of the Tom Lantos Tunnels.  More specific information regarding the Devil's Slide Trail can be found at visithalfmoonbay.org.

halfmoonbay.org on the Devil's Slide Trail

My hike was more of a trail run given the Devil's Slide is still a paved roadway.  I started actually past of the southern Devil's Slide trailhead facing the southern mouth of the Tom Lantos Tunnels.


From the Tom Lantos Tunnels the Devil's Slide Bunker can be seen to the south.  Said Bunker is actually a World War II observation station that was abandoned by 1949.  The land around the bunker apparently was stripped during a failed construction project in the 1970s.


My run began headed northward to the actual Devil's Slide trailhead over the former CA 1 right-of-way.




The Devil's Slide Trail traverses several steep road cuts before emerging out onto a wide bluff.




Along the coastal bluff the grade of the Devil's Slide Trail begins to rise steadily before coming to an observation area.







The Devil's Slide trail ends at the north parking lot trailhead which overlooks the bridges leading to the northern mouth of the Tom Lantos Tunnels.




Suffice to say the run back south on the Devil's Slide trail had some pretty scenic views from the relatively high grades.













The Devil's Slide Region was briefly covered on a prior blog containing the entire section of CA 1 between I-280 near San Francisco south to CA 17 in Santa Cruz.

November Bay Area Trip Part 7; California State Route 1 from I-280 south to CA 1780

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