Union River (Maine)

The Union River is a 21.9-mile-long (35.2 km) river that runs through Ellsworth, Maine. In the colonial era, it was known as the Mount Desert River.

The river forms at the north end of Graham Lake at the confluence of the river's East and West branches (44°43′48″N 68°23′04″W / 44.7300°N 68.3844°W / 44.7300; -68.3844 (Union River source)), on the border of the towns of Mariaville and Waltham. It runs south 13 miles (21 km) through Graham Lake to the dam at the lake's outlet, then continues south through Ellsworth, flowing through Leonard Lake and passing over its outlet dam just above the downtown. The Leonard Lake dam no longer serves any hydroelectric purpose but is kept in place to maintain the lake, upon which many camps have been built. At downtown Ellsworth, the river reaches tidewater, and flows south as an estuary for 5 miles (8 km) to its mouth at Union River Bay, on the border of Surry and Ellsworth, and thence into Blue Hill Bay.