The Lamoille River is a river which runs through northern Vermont and drains into Lake Champlain. It is about 85 miles (137 km) in length, and has a drainage area of around 706 square miles (1,830 km²). The river generally flows southwest, and then northwest, from the water divide of the Green Mountains, and is the namesake of Lamoille County, Vermont. The river's valley also gave its name to the now-defunct Lamoille Valley Railroad Company, successor to the St.