Grand River National Grassland is a protected prairie in northwestern South Dakota where the North and South forks of the Grand River meet, spanning parts of Perkins, Corson, and Ziebach counties and extending into the Standing Rock Sioux and Cheyenne River reservations. Its modern history follows northern plains settlement, Dust Bowl hardship, and federal land rehabilitation after many homesteads failed during the Great Depression. Formally designated in 1960, it includes mixed-grass prairie, river bottoms, badlands, buttes, sandstone outcrops, dunes, and claypan areas. The grassland supports broad ecological diversity, recreation near Blacktail Trail and Shadehill Reservoir, livestock grazing, and ongoing habitat restoration.