Claim: Lake Kampeska, an inland glacial lake in South Dakota connected to the 419 mile Big Sioux River (a tributary of the Missouri) was not discussed in Fremont and Nicollet's exploration notes of the Dakota Territory.
Evidence: Famous pathfinder John C. Fremont and scientist Joseph Nicollet explored this region of Dakota Territory approximately in May or June 1838. In their undated notes they described the area as the "lake country of the coteau prairie."