The Crow Creek massacre occurred in the early 14th century between American Indian groups in the South Dakota area. Crow Creek Site, the site of the massacre near Chamberlain, is an archaeological site and a U.S. National Historic Landmark. It is thought that either Middle Missou or Initial Coalescent Indians moved into the area. The overcrowding grew to a point that both sides conducted raids on each other's camps and mass graves produced the Crow Creek massacre.