Red Slate Mountain is a summit in the Sierra Nevada. It lies along the Sierra Crest that divides Fresno County from Mono County, California.Red Slate Mountain can be reached by scrambling either from McGee Pass, or starting from Bighorn Lake.The area to the north of Red Slate Mountain is amongst the most seismically active in California which is associated with the Long Valley Caldera.Red Slate Mountain was named by the California Geological Survey, in 1873.