The Five Mile River is a river approximately 23.5-mile (37.8 km) long, located in Connecticut's Northeast Corner. The original Nipmuc name was Assawaga, meaning "place between" or "halfway place." The Assawaga received its English name from the fact that the first land laid out upon it was "supposed to be about five miles from" Woodstock, Connecticut. The Five Mile is a tributary of the Quinebaug River and is part of the Thames River Watershed. Its source is Little Pond (also known as Schoolhouse Pond); close to the Massachusetts border. It empties into the Quinebaug River at Danielson, at the intersection of New England Interstate Route 12 and U.S. Route 6.
The Five Mile River has several dams, most of which are former mill operations. Its largest impoundment is Quaddick Reservoir, though there are several smaller dams including those that were built for the purpose of harnessing waterpower for industry. The best examples of surviving mills villages can be seen in Killingly; in villages such as Pineville, Ballouville, Attawaugan, and Dayville.