Lake Hanska, called “minne hanska” by the Sioux Indians meaning “long water,” occupies a basin formed 11,000 to 15,000 years ago by the Wisconsin glacier, with the original hard clay bottom now about 50 feet below the present water surface. The area south of the Little Cottonwood River was a favored place for Indians and is rich in legend and history, with evidence of prehistoric habitation in scattered burial mounds and an old Indian trail that once ran north of the lake. In the spring of 1863, Fort Hanska was built on a knob near this site as one of the fortified posts erected in southern Minnesota after the Sioux Uprising of 1862. Constructed by Company B, Ninth Minnesota Volunteers, the fort guarded the frontier between Madelia and the Big Cottonwood River and was protected by an earthen wall eight feet high topped with palisades. Soldiers in 1863 considered the post ideally located, 25 rods from the lake, with excellent swimming and fishing and a view over the countryside for a dozen miles in any direction.