Niagara River, River forming the U.S.-Canada boundary between western New York and southern Ontario. Its high flow and steep descent make it one of the best sources of hydroelectric power in North America. It connects Lake Erie with Lake Ontario, and Niagara Falls lies about halfway along its course. The U.S. and Canadian cities of the same name are on either bank of the river. It is navigable from Lake Erie to the upper rapids.
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