The mound appears on this 1856 map as Little Spirits Hill.

Spirit Mound was described by local Indigenous people to the Lewis and Clark expedition in 1804. Twenty years ago in 2001, it was replanted with native grasses and joined the South Dakota state park system as Spirit Mound Historic Prairie. In 2010, a geologic survey determined the mound to be a rock-cored drumlin created by a glacier. Check out the websites for Spirit Mound Trust or the Spirit Mound Historic Prairie for more information.

Both maps can be viewed in the Archives and Special Collections.
Information about the addition of Spirit Mound Historic Prairie to the South Dakota state park system can be found in the William J. Janklow papers at the Archives and Special Collections.
Geologic survey by Cody Miller, Origin and Erosion of Spirit Mound, http://www.spiritmound.com/PDF/Miller_spirit_mound.pdf (accessed November 8, 2021).