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Patterson Pass Road

Recently on a day trip to the San Francisco Bay Area I traversed the Diablo Range eastbound via Patterson Pass Road.


Patterson Pass Road is an approximately 13 mile roadway which starts at Mines Road in Livermore of Alameda County.  Patterson Pass Road eastward ascends over the approximately 1,600 foot namesake Patterson Pass into San Joaquin County where it ends at Interstate 580 near Tracy.  Patterson Pass Road has an infamous reputation as being a dangerous roadway due to the lengthy one-lane section and heavy rush-hour commute traffic.

Patterson Pass is one of the earliest documented European paths of travel over the Diablo Range as it was explored during the 1775-1776 Spanish Expedition led by Juan Bautista de Anza.  The 1775-1776 Spanish expedition charted out much of San Francisco Bay which led to the founding of the Presidio of San Francisco and Mission San Francisco de Asis.  Patterson Pass Road between Cross Road east to Midway Road is part of the Juan Bautista de Anza National Trail.  The Juan Bautista de Anza Trail is a 1,210 mile Auto Touring Route organized by the National Park Service which closely follows the 1775-1776 Spanish expedition from modern day Tubac, Arizona to the San Francisco Bay Area.  More information regarding the Juan Bautista de Anza National Historic Trail can be found on nps.gov and cahighways.org.

nps.gov on Juan Bautista de Anza National Historical Trail

cahighways.org on Juan Bautista de Anza National Trail in California

Patterson Pass ultimately didn't become part of the inland route of travel between the Spanish Missions on El Camino Viejo.  The route of El Camino Viejo was to the south over Corral Hollow Pass via what is now Signed County Route J2 on Tesla Road.   The earliest highway map I can find clearly showing Patterson Pass Road is a CSAA edition from 1917.

1917 CSAA State Highway Map

Patterson Pass Road can be seen on the 1935 California Division of Highways Mas of Alameda County.

1935 Alameda County Highway Map

My approach to Patterson Pass Road was from southbound Vasco Road in Livermore.  I made a left hand turn from Vasco Road onto Patterson Pass Road eastbound.



Patterson Pass Road between Vasco Road east to Greenville Road four-lanes and is directly north of Lawrence Livermore National Laboratory.



At Greenville Road the path of Patterson Pass Road drops to two lanes and exits the City of Livermore.



Patterson Pass Road east of Greenville Road to Cross Road has numerous road safety features.  Most of the traffic control measures seem to be oriented at slowing down commuter traffic.







East of Cross Road the alignment of Patterson Pass Road drops to a single lane and picks up the Juan Bautista de Anza National Historic Trail.  Patterson Pass Road is a wide single lane and quickly ascends to Patterson Past.














Patterson Pass has a wide shoulder that is worth pulling over to see as there is two wide vistas.  This view is from Patterson Pass looking west towards Livermore Valley.


The sharp descent in Patterson Pass Road eastward from the top of Patterson Pass is very dramatic to the eye.


From Patterson Pass almost all of the Altamont Pass Wind Farm can be seen.  The Altamont Pass Wind Farm was commissioned in 1981 and now consists of 4,930 wind mills which are capable of producing 576 Megawatts of electricity.


The eastward drop on Patterson Pass Road is fast and rolls through the hill side.


















As Patterson Pass Road approaches Midway Road the Altamont Pass Wind Farm sub-station can be seen at the former rail siding location Midway . Patterson Pass Road crosses under a Union Pacific rail underpass which originally part of the Western Pacific Railroad.






At Midway Road the Juan Bautista de Anza National Historic Trail splits off of Patterson Pass Road.  Patterson Pass Road expands back out to two-lanes approaching the San Joaquin County Line.



Patterson Pass Road continues eastward to I-580 as a normal two-lane roadway.





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