The Niagara River is not a river at all, but a strait. It meanders 36 miles north from the eastern tip of Lake Erie to the west end of Lake Ontario, draining the overflow from four Great Lakes. Twenty-two miles downstream from Buffalo and Fort Erie the river is split by Goat Island into two channels. It is here that the rapids begin. The river-bed drops fifty-five feet in less than a half mile and the water reaches speeds of up twenty-five miles per hour before reaching the edge of the Canadian Horseshoe, Bridal Veil and American Falls. From here it falls approximately 170 feet into the lower Niagara Gorge.
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river.
A strait is a naturally formed, narrow, typically navigable waterway that connects two larger bodies of water. Most commonly it is a channel of water that lies between two land masses.