Indian Grinding Rock State Historic Park

Indian Grinding Rock State Historic Park is a California State Park, preserving an outcropping of marbleized limestone with some 1,185 mortar holes—the largest collection of bedrock mortars in North America. It is located in the Sierra Nevada foothills, 8 miles east of Jackson. The park is nestled in a little valley 2,400 feet above sea level, with open meadows and large specimens of valley oak that once provided the Miwok peoples of this area with an ample supply of acorns. The 135-acre park was established in 1962 and listed on the National Register of Historic Places in 1971.

The native name for the site is "Chaw’se", the Miwok word for "grinding rock". Upon this rock they ground acorns and other seeds into meal, slowly forming the cup-shaped depressions in the stone, which can still be seen today.

Source: Wikipedia