Spirit Mound Historic Prairie is a state park in Clay County, South Dakota, featuring a prominent hill on the Great Plains. The Plains Indians of the region considered Spirit Mound the home of dangerous spirits (or “devils”). Members of the Lewis and Clark Expedition climbed the hill on August 25, 1804. The park was established in 2002, and is located about 6.5 miles north of Vermillion.

The local Indians were terrified of the hill, and would not venture anywhere near it (essentially considering it to be taboo). They believed that just a few decades earlier (some time in the mid-18th century), a band of several hundred Indian warriors, who had attacked the diminutive inhabitants of the mound, were massacred by the little people, who wielded magical arrows (the Indian band attempted to remove the presence of the already-hated little folk, who had dwelt there for many years, and were long perceived to be evil).

Due to extensive damming of the Missouri River, the summit of the Spirit Mound is one of the few precise places where historians know Lewis and Clark to have stood in that exact location.

The prairie surrounding the Spirit Mound has been planted with indigenous prairie grasses, in an attempt to restore the locale to its previous splendour. The area features an almost phenomenal array of insect life, a fact which was noted by the Lewis & Clark travel log over 200 years ago, and can reasonably be described as extremely scenic and beautiful. There is a trail about half a mile in length that leads up to the summit, and back down via a slightly different path. The trail crosses White Stone Creek (an idyllic tributary of the Vermillion River), which passes through the site.