Other federally recognized sites include the Little Bighorn National Monument, Bighorn Canyon National Recreation Area, Big Hole National Battlefield, and the National Bison Range. Department of the Interior Bureau of Land Management controls 8,100,000 acres (33,000 km) of 1.1 million acres of National Wildlife Refuges and waterfowl production areas in Montana. These lands are managed by the state for the benefit of public schools and institutions in the state.Approximately 31,300,000 acres (127,000 km) of wilderness in 12 separate wilderness areas that are part of the National Wilderness Preservation System established by the Wilderness Act of 1964. Montana is a large state with considerable variation in geography, topography and altitude, and the climate is, therefore, equally varied.The Pend Oreille River joined the Columbia River, which flows to the Pacific Ocean—making the 579-mile (932 km) long Clark Fork/Pend Oreille (considered a single river system) the longest river in the Rocky Mountains.The Northern Divide turns east in Montana at Triple Divide Peak, causing the Waterton River, Belly, and Saint Mary rivers to flow north into Alberta.In total, 77 named ranges are part of the Rocky Mountains.The eastern half of Montana is characterized by western prairie terrain and badlands.There they join the Saskatchewan River, which ultimately empties into Hudson Bay.
The western half is mountainous, interrupted by numerous large valleys.Montana is the 4th largest in area, the 8th least populous, and the 3rd least densely populated of the 50 U. Smaller island ranges are found throughout the state. The western half of Montana contains numerous mountain ranges.Wyoming is to the south, Idaho is to the west and southwest, have extensive agricultural resources and multiple opportunities for tourism and recreation.East and north of this transition zone are the expansive and sparsely populated Northern Plains, with tableland prairies, smaller island mountain ranges, and badlands.