This climb ranks #11 on the Tri-County Top Climbs List with Fiets Index of 3.93. However, since just over two-thirds of the climb is gravel and dirt on very steep grades, the difficulty exceeds its base Fiets Index. The ride is not very scenic, but is certainly challenging. We recommend a cross bike or at the very least a comfortable road bike with 28mm tires.
Western Mine Road becomes Ida Clayton Road towards the top of the climb (around mile 3) and you can continue along a rough rolling roadway for another 3 miles to the beginning of the 4 mile Ida Clayton descent - at the bottom is Hwy 128 in Sonoma County.
Where’s the name come from? The Great Western Quicksilver Mine (a mercury mine) was accessed by this road. The mine produced continuously from 1873 to 1909. See, Roaming the Backroads of California by Peter Browning, p. 68:
“About six miles from the summit turn left on Western Mine Road. It's narrow and winding, but don't be put off — it's perfectly good for any sort of passenger car, though not for recreational vehicles and trailers. The first mile is paved, followed by three miles of good gravel surface to the summit at the Sonoma County line. Fifteen to twenty miles per hour is all the road is good for. About two miles along, in an open area downhill from the road, was the former Great Western Quicksilver Mine, which produced continuously from 1873 to 1909.”
Descent: We recommend against descending this road on anything short of a cross or mountain bike. During the summer, the temperatures in this area can approach and exceed 100 degrees, so beware of the weather.
Supplies: Middletown is just a few miles from the start of this climb and all supplies necessary for the ride are available there.
Roadway surface/Traffic: The roadway is in poor condition and gravel much of the climb. It is unlikely you will encounter more than a handful of vehicles (likely four wheel drive) on this climb