Back River (Powwow River)
Coordinates: 42°51′20″N 70°55′39″W / 42.8556°N 70.9274°W The Back River is a 6.5-mile-long (10.5 km) river located in New Hampshire and Massachusetts in the United States. It is a tributary to the Powwow River, part of the Merrimack River watershed. Approximately 3.0 miles (4.8 km) of the river are in New Hampshire,[1] with the remaining 3.5 miles (5.6 km) in Massachusetts.
The Back River rises in Kensington, New Hampshire and flows southeast, almost immediately entering the town of South Hampton. The river turns south and enters Amesbury, Massachusetts, joining the Powwow River at tidewater just downstream from the city's center at the falls of the Powwow.