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.