Indian Grinding Rock State Historic Park

Indian Grinding Rock State Historic Park is a state park unit of California, United States, 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 (13 km) east of Jackson. The park is nestled in a little valley 2,400 feet (732 m) 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 (55 ha) park was established in 1962^[3] and listed on the National Register of Historic Places in 1971.

• http://en.wikipedia.org/wiki/Indian Grinding Rock State Historic Park