Montana is a state in the Mountain West subregion of the Western United States. It is bordered by Idaho to the west; North Dakota and South Dakota to the east; Wyoming to the south; and by the Canadian provinces of Alberta, British Columbia, and Saskatchewan to the north. It is the fourth-largest state by area, the seventh-least populous state, and the third-least densely populated state. The western half of Montana contains numerous mountain ranges, while the eastern half is characterized by western prairie terrain and badlands, with smaller mountain ranges found throughout the state. In all, 77 named ranges are part of the Rocky Mountains.