Niagara Falls, a spectacular waterfall in the NIAGARA RIVER, is the world's greatest waterfall by volume at 2832 m3. It is split in two by Goat Island. The American Falls are 59 m high (21-34 m to rock debris at the base of the falls) and 260 m wide and carry about 10% of the flow. The Canadian, or Horseshoe, Falls are 54 m high and 670 m wide, with the remaining 90% of the flow. However, only the Canadian Falls fall freely to the Maid-of-the-Mist pool, where they have excavated a pool as deep or deeper than they are tall. The falls were formed some 14 000 years ago as retreating glaciers exposed the NIAGARA ESCARPMENT, permitting the waters of Lake ERIE, which formerly drained south, to flow northward into Lake ONTARIO.

The falls have eroded the soft shales and limestones of the escarpment at an average rate of 1.2 m per year and now stand 11 km from their place of origin at present-day QUEENSTON. Their recession rate has been variable though, as the volume of water flowing from the upper Great Lakes controls it. Because of changing land and lake levels in northern Ontario, the flow through the Niagara River was reduced to 10% of its present volume for a period of 5000 years. During this time the falls were almost stationary.

Niagara Falls were of spiritual significance to the native people, such as the NEUTRALS. The name is of native origin and most likely describes either the falls, "thunder of the waters", or the river, "on or at the neck."

The awesome spectacle was first described by Louis HENNEPIN, who saw the falls in 1678, calling them "a vast and prodigious Cadence of Water." Among those who tried to describe their effect was Charles Dickens, who wrote, "I seemed to be lifted from the earth and to be looking into Heaven." With tourism, which began in the 1800s, came daredevils who defied the falls in barrels, boats and rubber balls. The most celebrated was The Great Blondin, who performed on a tightrope over the gorge (1859). Stunting was outlawed in 1912.

To save the area from hucksters and speculators, Ontario created Queen Victoria Park in 1885 - Canada's first provincial PARK. That same year a similar public park was created on the American bank. Millions of tourists visit the area every year, viewing the falls from several towers, a tunnel beneath Horseshoe Falls, for helicopter rides, a cable aerocar over the whirlpool, a jet boat through the lower rapids and the Maid of the Mist, a boat that carries sightseers to the foot of the falls.

International agreements control the diversion of water for HYDROELECTRIC power, which was first generated on the Canadian side of the river in 1893. The Niagara Diversion Treaty (1950) stipulated that a minimum flow of 50% be reserved for the falls during daylight hours in the summer and that the rest, up to 75% overnight and during the winter, be divided equally between Canada and the US. In Canada water is diverted from the Niagara River above the falls and fed into the turbines of Sir Adam Beck Generating Stations No 1 and No 2 by canals and tunnels, after which the water is returned to the river.