Writing Rock State Historic Site in northwestern North Dakota preserves two granite boulders carved with Indigenous petroglyphs, among the state’s notable surviving rock art sites. The carvings center on thunderbirds, powerful beings in many Plains traditions, and were likely made sometime between 1000 and 1700 by pecking and grinding the stone with harder tools. Although their full meaning is no longer known, both Sioux and Assiniboine peoples regarded the place as sacred. Writing Rock also reflects a broader northern Plains rock art tradition found across surrounding states and provinces. After years at the University of North Dakota, the smaller boulder was returned in 1965, and both stones are now protected within a shelter.