High Quality Content by WIKIPEDIA articles! The Devils River (also known archaically as the Manitoo River) is a small 12-mile (19 km) long river in the state of Wisconsin in the United States. Devils River flows primarily through Brown and Manitowoc counties, and joins with the Neshota River to form the West Twin River. It is part of the 176-square-mile (460 km2) West Twin River watershed.