Cycling Pine Flat Road -- Sonoma County’s fourth most difficult bike climb.
Ride 11.2 miles to 3,158’ gaining 3,589’ at 4.9% average grade.
This climb ranks #7 on the Tri-County Top 25 list with a Fiets Index of 4.44. The first seven miles of Pine Flat (to “the guardrail” as the locals refer to it) are a modest ascent at 5.5% average grade, followed by 2.1 miles that actually averages -0.8% grade (perhaps where the "flat" part of the road's name comes from). The biggest challenge of this climb comes towards the end, with the last 2.2 miles averaging 9.2%, with 1.1 mile at the beginning of that stretch averaging 11.4% (20% for a brief time on "The Wall" at the 10.1 mile mark.) The upper portion of the ride approaches The Geysers area and can be torturously hot in the summer.
Pine Flat is located in the Mayacamas Mountains, which stretch 52 miles from Clear Lake to northern Sonoma and Napa counties.
Looking back from the start via drone aerial photo.
First stretch of Pine Flat Road.
Lower portion of the climb.
Aerial drone panorama of mile three to finish.
Cyclist on “The Wall”.
“The Wall” -- ¼ mile at 16% beginning at mile 10.2.
Read it and weep -- the Garmin don’t lie!
Peak gradient on “The Wall”.
Section just after The Wall.
The first 5.5 miles (to the pond) offer magnificent vineyard views along Pine Flat Road, while the next 1.5 miles give us views of the Alexander Valley to the west, Mt. St. Helena to the southeast (photo) and, if we look carefully and know what we are looking for, Mt. Tamalpais to the south (photo).
Supplies: The Jimtown Store is less than a mile from the start of the ride.
Roadway surface and traffic: The roadway is in decent condition at the bottom, with moderate deterioration towards the top. Caution is required for the decent as the upper portion of the mountain is very steep with rough road, sharp turns and gravel in many locations. Traffic over the entire climb is minimal.
A LITTLE HISTORY
Old structure at the start of the climb.
There were hundreds of mercury (“quicksilver”) permits drawn in the 1870s, and many active mines operating in Sonoma County in the late 19th and early 20th centuries. The last mine to close was the Mount Jackson Mercury Mine, located in Guerneville, on Sweetwater Springs Road which operated from 1889 to 1972. The largest mining town was Pine Flat, which grew up around the mercury mine in that area. (Santa Rosa Press Democrat, July 11, 2010 “The Lasting Impact of Mercury”) and in its hayday consisted of 60 homes, three hotes, two dry goods stores, a fruit vendor, bakery, lumber yard, two shoe shops, two laundries and six saloons -- no churches or schools, however! The structure pictured above may be related to the Pine Flat mining town, although the original town was located three to four miles up Pine Flat Road, and there are no obvious signs of the town remaining.
Photo in this section: Pressdemocrat.com Boomtown’s or Bust, Clark Mason, December 12, 1914.
Photo courtesy of Healdsburg Museum.
In the 1870s, Pine Flat may have been the fastest growing town in Northern California, born of the mercury boom during that time. Pine Flat’s population in the 1870s is estimated at 1,000-4,000. 70 claims were filed in this area, known as Cinnabar Mining District, with colorful names such as Fandango, Mohawk, Socrates and Rattlesnake. The Press Democrat’s article Boomtown’s or Bust, by Clark Mason, is quite entertaining and a good read for those interested in Sonoma County History.