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November Bay Trip Part 2; Mount Diablo State Park

The Diablo Range is a long inland Californian Coastal range stretching from the Carquinez Straight near San Francisco Bay south to the Temblor Range roughly bounded by California State Route 46. I've been down pretty much almost every major road in the Diablo Range over the years, some are among my favorites like CA 198 and the Parkfield Grade.  There has been two major roads I had left to explore in the Diablo Range that I've been meaning to get off my list of things to do.  First is Idria Road to the Idria Mine and the Summit Road of Mount Diablo in Mount Diablo State Park.






After jumping onto I-580 after completing I-205 I took I-680 north to Diablo Road.





I took Diablo Road to Mount Diablo Scenic Boulevard which runs to the southern entrance of the State Park becoming South Gate Road.







Mount Diablo is a 3,849 peak in the northern Diablo Range.  While not the tallest peak in the Diablo Range Mount Diablo has a prominence of 3,109 feet which gives it one of the widest vistas in all of California.  Mount Diablo is the tall mountain that can be seen east of the Golden Gate Bridge behind San Francisco Bay and Oakland.

Mount Diablo is accessed via the Summit Road which is reached by the South Gate Road from the south and the North Gate Road from the north.  The South Gate Route is 10.5 miles from the state park entrance and averages a 5.8% grade on a 3,169 foot ascent.  The North Gate Road route is 12.4 miles long from the state park entrance and averages a 6% grade on a 3,687 foot ascent.  The vital statistics I just cited were obtained from Pjammey Cycling which is probably the best place to get grade information on notable Californian roadways.  The link below even has a handy map of both the South and North Gate Roads.

Pjammey Cycling on Mount Diablo

Given I just cited a cycling website you'd might imagine the road is popular for cyclists and you'd certainly be correct about that.  Signage warns drivers constantly to be leery of Cyclists.  My ascent to Mount Diablo was on the South Gate Road while my descent was on the North Gate Road.





The 1,000 foot line is reached quickly on the South Gate Road.





The South Gate Road has a ton of open vistas along sweeping cliff-side roadways that utilize numerous hairpins.


The actual gate on South Gate Road is actually several miles into Mount Diablo State Park.


Mount Diablo finally starts to come into view, the Summit Road really does go all the way to the top.





The South and North Gate Roads meet at the Walnut Creek Ranger Station which is about 2,000 feet above sea level.


The Summit Road is only 4.3 miles long but gains the bulk of the elevation up to Mount Diablo.  Apparently the average grade on the Summit Road is 6.7% but there is definitely a spot or two near the top over 10%.





The drive to the top of the Summit Road isn't fast with 15-20 MPH speed limits but it is plenty wide and well engineered.  I wasn't hurting for passing room for bikes or oncoming traffic on the ascent up to the summit.









The actual top of Summit Road is the actual 3,849 peak of Mount Diablo.


There is one hell of a view looking back south at all the switchbacks along Summit Road.  It reminds me of a miniature Pikes Peak Highway.






The views of the area were kind of obstructed eastward with a cloud hanging over the summit.






Part of Mount Diablo was acquired for State Park use in 1921 but it wasn't until 1931 that enough land was annexed before the park was formally dedicated.  The Summit Building was built sometime in the 1930s.





The drive back down to the Walnut Creek Ranger Station is stunning.  I used 1st gear most of the way down off the Summit Road given the speed limit was so low that I didn't feel a need to use my brakes up.












The North Gate Road is far less daunting than the South Gate Road.  There are a couple hairpins but they are far wider than the South Gate Road.  There was some minor road damage along the North Gate Road but nothing too out of control.  Unlike the South Gate Road the actual gate is at the state park boundary.











According to the Mount Diablo State Park brochure North Gate, South Gate, and Summit Road were all opened as stage routes in 1874.  Apparently the roads were closed sometime in the 1890s and reopened again by 1915.

Mount Diablo State Park Brochure

All three roads are clearly seen on the 1935 California Division of Highways map Contra Costa County as under county maintenance.

1935 Contra Costa County Map






 

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