The Hudson then flows south, taking in Beaver Brook and the outlet of Lake Harris. After its confluence with the Indian River, the Hudson forms the boundary between Essex and Hamilton counties. In the hamlet of North River, the Hudson flows entirely in Warren County and takes in the Schroon River. Further south, the river forms the boundary between Warren and Saratoga Counties. The river then takes in the Sacandaga River from the Great Sacandaga Lake. Shortly thereafter, the river leaves the Adirondack Park, flows under Interstate 87, and through Glens Falls, just south of Lake George although receiving no streamflow from the lake. It next goes through Hudson Falls. At this point the river forms the boundary between Washington and Saratoga Counties.[10] Here the river has an elevation of 200 feet (61m).[6] Just south in Fort Edward, the river reaches its confluence with the Champlain Canal,[10] which historically provided boat traffic between New York City and Montreal and the rest of Eastern Canada via the Hudson, Lake Champlain and the Saint Lawrence Seaway.[16] Further south the Hudson takes in water from the Batten Kill River and Fish Creek near Schuylerville. The river then forms the boundary between Saratoga and Rensselaer counties. The river then enters the heart of the Capital District. It takes in water from the Hoosic River, which extends into Massachusetts. Shortly thereafter the river has its confluence with the Mohawk River, the largest tributary of the Hudson River, in Waterford.[6][10] The river then reaches the Federal Dam in Troy, marking an impoundment of the river.[10] At an elevation of 2 feet (0.61m), the bottom of the dam marks the beginning of the tidal influence in the Hudson as well as the beginning of the lower Hudson River.[6]