Merriam-Webster Collegiate Dictionary - niagara falls

 geographical name  1. waterfalls on border between New York & Ontario in the Niagara River (36 miles or 58 kilometers flowing from Lake Erie N into Lake Ontario); divided by Goat Island into Horseshoe, or Canadian, Falls (158 feet or 48 meters high) & American Falls (167 feet or 51 meters high)  2. city W New York at the falls population 55,593  3. city Canada in SE Ontario population 78,815