Niagara Falls is the collective name for three waterfalls American Falls, Horseshoe Falls and Bridal Veil Falls – that straddle the international border between Canada and the United States; more specifically, between the province of Ontario and the state of New York.
Niagara Falls were formed when glaciers receded at the end of the Wisconsin glaciation (the last ice age). Water stems from the upper Great Lakes and the river is estimated to be 12,000 years old. While not exceptionally high, the Niagara Falls are very wide. More than six million cubic feet (168,000 m3) of water falls over the crest line every minute in high flow, and almost four million cubic feet (110,000 m3) on average.
About 10,900 years ago, the Niagara Falls was located between present-day Queenston, Ontario, and Lewiston, New York, but erosion of their crest has caused the waterfalls to retreat approximately 6.8 miles (10.9 km) southward. The Horseshoe Falls, which are approximately 2,600 feet (790 m) wide, have also changed their shape through the process of erosion; evolving from a small arch, to a horseshoe bend, to the present day gigantic V. Until the 1950s, when the flow of water began to be controlled, the brink of the falls moved backward an estimated three feet every year because of erosion.
The Niagara Falls are renowned both for their beauty and as a valuable source of hydroelectric power. Twelve million tourists from all over the world visit Niagara Falls every summer.