The Niagara River flows north from Lake Erie to Lake Ontario, forming part of the border between Ontario, Canada, to the west, and New York, United States, to the east. The origin of the river's name is debated. Iroquoian scholar Bruce Trigger suggests it is derived from a branch of the local Neutral Confederacy, referred to as the Niagagarega people on several late-17th-century French maps. George R. Stewart posits that it comes from an Iroquois town named Ongniaahra, meaning "point of land cut in two."

Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorge, spanning the border between the province of Ontario in Canada and the state of New York in the United States. The largest of the three is Horseshoe Falls, which straddles the international border of the two countries. It is also known as the Canadian Falls. The smaller American Falls and Bridal Veil Falls lie within the United States. Bridal Veil Falls is separated from Horseshoe Falls by Goat Island and from American Falls by Luna Island, with both islands situated in New York.