The town's namesake, the boulder Mistusinne (also spelled Mistaseni), was a 400-ton glacial erratic and a sacred gathering place for the Cree and Assiniboine peoples. During the South Saskatchewan River Dam Project, it was in the flood path to the new reservoir of Lake Diefenbaker. In 1966, the Prairie Farm Rehabilitation Administration had the rock blasted apart with explosives, despite efforts by groups to save it. Pieces of the rock were used in monuments to Chief Poundmaker and a memorial to the boulder itself in Elbow. Large fragments were located under the waters of the lake in 2014.