Indian Grinding Rock State Historic Park (IGR) is located in the Sierra Nevada foothills 12 miles east of Jackson, CA. The park nestles in a little valley 2,400 feet above sea level with open meadows and large valley oaks that once provided the Native Americans of this area with an ample supply of acorns. The park was created in 1968 and preserves a great outcropping of marbleized limestone with some 1,185 mortar holes -- the largest collection of bedrock mortars in North America.