Niagara Falls, in the Niagara River, W N.Y. and S Ont., Canada; one of the most famous spectacles in North America. The falls are on the international line between the cities of Niagara Falls, N.Y., and Niagara Falls, Ont. Goat Island splits the cataract into the American Falls (167 ft/51 m high and 1,060 ft/323 m wide) and the Horseshoe, or Canadian, Falls (158 ft/48 m high and 2,600 ft/792 m wide). The governments of the United States and Canada control the appearance of the surrounding area, much of which has been included in parks since 1885.
The earliest written description of the falls is that of Louis Hennepin (in Nouvelle Découverte, 1697), who was with the expedition of Robert Cavelier, sieur de La Salle, the French explorer, in 1678. In the 19th cent., daredevils attempted to brave the falls in barrels, boats, and rubber balls. The great Blondin performed (1859) on a tightrope over the falls, which continue to be a major center of international tourism. Historical and natural history material relating to the region is in the Niagara Falls Museum in the city of Niagara Falls, N.Y.
The falls were formed c.10,000 years ago as the retreating glaciers exposed the Niagara escarpment, thus permitting the waters of Lake Erie to flow north, over the scarp, to Lake Ontario. The escarpment has been gradually eroded back toward Lake Erie, a process that has formed the Niagara Gorge (c.7 mi/11 km long); the Whirlpool Rapids and the Whirlpool are there. Horseshoe Falls is eroding upstream at a faster rate than the American Falls because of the greater volume of water passing over it. A great rock slide occurred (1954) at the American Falls and formed a huge talus slope at its base. Water was diverted from the American Falls for several months in 1969 by the U.S. Army Corps of Engineers to study the bedrock and to remove some of the talus.
International agreements control the diversion of water for hydroelectric power; weirs divert part of the flow above the deeper Canadian Falls to supplement the flow in the shallower American Falls. Hydroelectric-power developments were authorized under the Niagara Diversion Treaty (1950), which stipulated a minimum flow to be reserved for the falls and the equal division of the remaining flow between the United States and Canada. In the United States the project was undertaken by the Power Authority of the State of New York. Water is diverted from the river above the upper rapids into underground conduits (46 ft/14 m wide and 66 ft/20 m high). It is then conveyed overland, dropping 314 ft (96 m) to a point below the lower rapids where, as it returns to the river, the water passes through turbines that power 13 generators of the Robert Moses Niagara Power Plant (1,950,000-kW capacity; opened 1961). Associated with the New York hydroelectric-power project is the construction in the area of new roads, bridges, and parks.
In Canada the project was undertaken by the Hydro-Electric Power Commission of Ontario. Water is diverted from the river above the falls and is fed into the Sir Adam Beck Generating Stations (1,775,000 kW; 1954) by way of a series of tunnels and canals.
