Niagara

River that flows along the border between the state of New York, USA, and Ontario, Canada, from Lake Erie, over the Niagara Falls, and into Lake Ontario; length 56 km/35 mi. It is navigable for 32 km/20 mi above the Falls, and again in its lower 11 km/7 mi from Lewiston, New York, to Lake Ontario.

Course The river issues from Lake Erie between Buffalo, New York, and Fort Erie, Ontario, and flows north, around Grand Island, over the Falls, through a 6-km/4-mi canyon, emerging at Queenston, Ontario, and entering Lake Ontario between Niagara-on-the-Lake, Ontario, and Youngstown, New York. Youngstown is the site of Old Fort Niagara (1726), central to the British–French power struggles, and thought to be the oldest European building on the Great Lakes.

Bridges, dams, and conduits The Rainbow International Bridge (1941) spans the gorge between Niagara Falls, New York, and Niagara Falls, Ontario. Another bridge across the river is the Peace Bridge at Buffalo. Dams and conduits have been built to divert water from above the falls to large power developments downstream. The flow over the falls is cut back at night and increased during the day for scenic purposes; 94% of the water is carried over the Horseshoe Falls.