The entire county lies within the Little Miami River watershed, with the exception of extreme eastern areas, which are within the Scioto River watershed. Clinton County lies within the till plains physiographic region, and is somewhat flat or gently rolling. The northern two thirds of the county were covered with an ice sheet during the Wisconsinan Stage, while the southern third was covered by ice sheets during the much older Illinoian Stage. Because of such a history with ice, glacial features are readily found on the landscape, such as moraines and kames.