Indian Grinding Rock State Historic Park is named for its impressive chaw'se. Chaw'se is the Miwok word for "grinding rock" – a slab of marbleized limestone on which the Miwok ground acorns into meal. Over thousands of years, this grinding formed 1,185 cup-shaped depressions in the stone. This is the largest collection of bedrock mortars anywhere in North America.
Along with the mortar holes, the chaw'se also features 363 petroglyphs (carved images), estimated to be 2,000 to 3,000 years old: circles, spoked wheels, animal and human tracks, wavy lines, and so on. Some of these carvings are now becoming difficult to see.
This association of rock art and bedrock mortar holes is unusual in California.