Little Missouri National Grassland is a vast protected area of prairie and badlands in western North Dakota and, at 1,028,051 acres, the largest national grassland in the United States. Part of the Dakota Prairie Grasslands, it includes a landscape of mixed-grass prairie, deeply eroded badlands, and the winding Little Missouri River, with Theodore Roosevelt National Park lying within its broader boundaries under separate management. Its patchwork includes public, state, and private lands, much of it leased for cattle grazing. The area is important for its scale, distinctive northern Great Plains scenery, and the environmental pressures posed by oil and gas development.