When people ask about, "The Falls of Niagara" some are surprised to learn there are really 3 falls at Niagara. They are, the American Falls, The Bridal Veil Falls and the Canadian Horseshoe Falls. As you look at these falls from Queen Victoria Park on the Canadian Side of the border you might wonders who own these falls. Well, here's the answer. The Treaty of Ghent, signed on Christmas Day in the City of Ghent, Belgium set out the terms that ended the War of 1812-14 between Canada (Britain) and the United States. The agreed boundary between Canada and the United States was the middle of the Niagara River. If you look at a map you will see the American Falls and Bridal Falls are totally in the United States. The Canadian Horseshoe Falls is located in Canada. So, there's your answer.
Attached is a map of the International Boundary. You'll find this map plus lots more interesting facts about Niagara Falls in a fascinating book entitled, Tommy Trent Presents, An Exciting Activity/Comic Book, The Niagara Falls Mystery.