Kimmswick Bone Bed, now within Mastodon State Park, contains late ice-age bone deposits in an area of less than five acres, with up to 11 feet of excavated deposits preserving evidence of animals from the late Pleistocene Epoch to the early Holocene Epoch. Evidence of Indians with mastodon is confined to the upper 3 feet of the deposit, about 18 to 36 inches below the surface, in two Clovis layers separated by a noncultural zone. The site is significant to both archaeology and paleontology, fields that rarely overlap except in the late Pleistocene and early Holocene, when men first appeared in North America at the end of the ice age, and both fields depend on careful excavation, recordkeeping, and contributions from other sciences to preserve information as digging destroys the site itself. Excavations by Illinois State Museum staff in 1979 revealed the first undisputed evidence in the United States of an association between early Indians and mastodon, bringing the site international attention, and in 1980 it was listed on the National Register of Historic Places because it provided the first solid evidence for association of the Llano Complex (Clovis) and the American mastodon. A local effort to save the bone bed began in 1970, accelerated with the formation of the Mastodon Park Committee in 1974, raised part of the acquisition money through a fund drive with the state providing the rest, and led to the property's acquisition in 1976 by the Missouri Department of Natural Resources and its addition to the state park system.