The Ohio River Story - Part I (GM-23)
Before the glacial age, the pattern of stream drainage in Indiana was greatly different from what it is today. A major stream, called the Teays River by geologists, flowed from West Virginia across Ohio and northern Indiana to join the preglacial Mississippi River in northern Illinois. But about a million years ago, one of the first of several glaciers that was to spread across northern Indiana buried the Teays Valley beneath hundreds of feet of clay and gravel. The Ohio River is part of a newly formed drainage system created by these glaciers and the meltwaters that flowed from them.

Our Hoosier State Beneath Us: Geomorphology