Topographically, part of the county is situated on the western foothills of the Appalachian Mountains. The county contains four small lakes, Lake Waterloo near Waterloo, Lake Boivin in Granby Township, Lake Roxton in Roxton Township, and Lake Stukely in Stukely Township. All of the lakes flow into the Yamaska River, except for Lake Stukely which feeds into the St-François River, both of which flow northwards and are tributaries to the Saint Lawrence River. A prominent feature of the county is Mount Shefford in the Township of Shefford, one of a series of the Monteregian Hills that lie in a line between the Appalachian Mountains and the Saint Lawrence River.