A fire July 3, 2006, burned 1,998 acres (8.09 km2) near Moccasin Powerhouse according to the California Department of Forestry.

Construction on the original Moccasin Powerhouse, designed by San Francisco architect Henry A. Minton, was started in Fall 1921.

During the Gold Rush, the locale was a stage coach stop on Big Oak Flat Road.

Old Priest Grade, a narrower road and predecessor to the current route of SR120, covers the same change in elevation over about 1.8 miles (2.9 km).

A sign on Highway 120 also advises drivers to turn off air conditioning in order to prevent overheating while climbing either grade.

Locals tell stories of car accidents in history where the vehicles left the path of Old Priest Grade and tumbled into Grizzly Gulch.

[citation needed] Construction to widen curves and add guard rails began in July 2010.