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, 8mi east of Jackson. The park is nestled in a little valley 2400ft 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 135acre 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. Along with the mortar holes, the main grinding rock within the park features a number of petroglyphs: circles, spoked wheels, animal and human tracks, wavy lines, etc. Some of these carvings are thought to be as much as two or three thousand years old and are now becoming difficult to discern. This association of rock art and bedrock mortar pits is unique in California. Except for one other small site, Chaw'se has the only known occurrence of mortars intentionally decorated with petroglyphs.
