From Ohio History Central
When early glaciers advanced southward across Ohio during the Pleistocene Ice Age, they destroyed drainage systems. One of these rivers was the Teays River, which in preglacial times, flowed northward across WestVirginia and entered Ohio near Portsmouth. When ice blocked the Teays in the vicinity of Chillicothe, a large lake formed in the valley of the Teays River and its tributary valleys. This lake was named for William G. Tight, who studied the Teays River. As the lake waters rose, they eventually spilled over a low divide and formed a new drainage system that eventually would become the Ohio River we know today.