From Ohio History Central
In the classic division of the Pleistocene Ice Age, the Illinoian glacier was the third of four major glacial advances. It is estimated that this glaciation began about 300,000 years ago. The Illinoian glacier advanced farther south than the most recent (Wisconsinan) glacier and its thin, highly weathered sediments are preserved in a narrow band in southwestern, southcentral and northeastern Ohio. Sand and gravel outwash from the Illinoian glacier is preserved as high terraces along some major river valleys such as the Scioto and Hocking.