31. Horseshoe Falls, Ontario (Niagara)
From largest to smallest, the three waterfalls are the Horseshoe Falls, the American Falls and the Bridal Veil Falls. The Horseshoe Falls lies on the border of the United States and Canada with the American Falls entirely on the American side, separated by Goat Island. The smaller Bridal Veil Falls are also on the American side, separated from the other waterfalls by Luna Island. The international boundary line was originally drawn through Horseshoe Falls in 1819, but the boundary has long been in dispute due to natural erosion and construction.