Cedar River National Grassland is a protected tract in southern North Dakota within the U.S. National Grassland system. Encompassing 6,717 acres in Sioux and Grant counties, it includes a section in Sioux County that lies within the Standing Rock Sioux Reservation. Its terrain combines level plains, rolling hills, dry streambeds, and a few small flowing streams. The grassland is administered by the U.S. Forest Service as part of the Dakota Prairie Grasslands, with offices in Bismarck and local ranger services shared with Grand River National Grassland from Lemmon, South Dakota.