Paleoindians sometimes hunted mastodons until these giant mammals died out at the end of the Ice Age.

Without question the most significant and well-known extinct Ice Age animal found in Ohio was the American mastodon, Mammut americanum. Although most specimens consist of isolated teeth or tusks, a number of nearly complete specimens have been found. Several are on display at museums in the state, including the famous Conway mastodon displayed at the Ohio Historical Society. Mastodons were elephantlike animals that were sturdily built browsers of open spruce forests. Adults stood about nine feet high at the shoulder and they weighed between four and five tons. Their cone-shaped teeth are distinctive. Most complete specimens have been found in the sediments of former glacial lakes where they broke through the ice in winter or became bogged down in mud. Some specimens show evidence of having been butchered by Paleoindians.

Mammoths were elephants that are related to the modern Indian elephant. They were more slimly built than mastodons and were primarily grazing animals more common to grasslands. Although mammoth remains are not uncommon in Ohio, they are decidedly less common than are the remains of mastodons. Two species of mammoth have been recognized in Ohio: Mammuthus primigenius, the northern mammoth, and Mammuthus columbi, a more southerly species. Both mastodons and mammoths became extinct about 10,000 years ago.