Writing Rock State Historic Site, located twelve miles (19 km) northeast of Grenora, North Dakota in Divide County near the Montana border, is the site of two large granite boulders, carved with petroglyphs featuring thunderbirds, mythological creatures that are of importance in the culture of Plains Indian tribes.
For many years, that smaller boulder was kept at the University of North Dakota, but in 1965, it was returned to what had by then become the Writing Rock State Historic Site.
Similar rock art sites are found in Roche Percee and Kamsack, Saskatchewan; Longview and Writing-on-Stone Provincial Park, Alberta; Pictograph Cave near Billings, Montana; Dinwoody, Wyoming; Ludlow Cave at Buffalo, South Dakota; and at numerous archeological sites in the upper midwestern United States.
Thunderbirds, mythological creatures responsible for lightning and thunder, are central to stories told by Algonquian-speaking and Siouan-speaking tribes.
A massive, flying bird surrounded by interconnected lines and circles covers the flattest side of the boulder.