Niagara Falls. Niagara Falls from the Canadian side of the American-Canadian border. Seen here is the Canadian Horseshoe Falls, the larger of the two main falls. It is 49 metres (m) high and 790 m long along the crest. The Horseshoe Falls carry about 90% of the 5.5 million litres of water which flow over the Niagara Falls each second. The Falls first formed about 12,000 years ago where the Niagara River flowed over an escarpement as it travelled from Lake Erie to Lake Ontario. The Falls have since retreated, forming a gorge 11 kilometres long. The first European to visit the Falls was probably Samuel de Champlain in 1613. The Falls are now a major tourist attraction.