Coordinates: 45°00?29?N 71°30?15?W? / ?45.0081°N 71.5043°W? / 45.0081; -71.5043 Halls Stream is a 25.2 mile long (40.5 km)[1] tributary of the Connecticut River. For most of its length, it forms the boundary between Canada and the United States, with the province of Quebec to its west and the state of New Hampshire to its east.