The Minidoka Dam is an earthfill dam in the western United States, on the Snake River in south central Idaho. Completed 116 years ago in 1906, the dam is east of Rupert on county highway 400; it is 86 feet (26 m) high and nearly a mile (1.6 km) in length, with a 2,400-foot (730 m) wide overflow spillway section. Minidoka Dam and power plant were listed on the National Register of Historic Places in 1974. Walcott Park, close to the dam, is a popular summertime picnic area. Lake Walcott State Park and the headquarters for the Minidoka National Wildlife Refuge are adjacent to the dam.