Kartchner Caverns State Park is a state park of Arizona, United States, featuring a show cave with 2.4 miles (3.9 km) of passages. The park is located 9 miles (14 km) south of the town of Benson and west of the north-flowing San Pedro River. Long hidden from view, the caverns were discovered in 1974 by local cavers, assisted by state biologist Erick Campbell who helped in its preservation. The park encompasses most of a down-dropped block of Palaeozoic rocks on the east flank of the Whetstone Mountains.