Mastodon State Historic Site is a publicly owned, 431-acre (174 ha) archaeological and paleontological site with recreational features in Imperial, Missouri, maintained by the Missouri Department of Natural Resources, preserving the Kimmswick Bone Bed. Bones of mastodons and other now-extinct animals were first found here in the early 19th century. The area gained fame as one of the most extensive Pleistocene ice age deposits in the country and attracted scientific interest worldwide.

The site was purchased by the state in 1976 following an effort to preserve it from destruction with the construction of Interstate 55. Archaeological history was made at the site in 1979 when scientists excavated a stone spear point made by hunters of the Clovis culture (14,000–10,000 years ago) in direct association with mastodon bones. This was the first solid evidence of the coexistence of people and these giant prehistoric beasts. The Kimmswick Bone Bed was added to the National Register of Historic Places in 1980.