Ottawa River

Ottawa River

River, eastern central Canada, the chief tributary of the St. Lawrence River. It rises in the Laurentian plateau of western Quebec and flows west to form the Quebec-Ontario border before joining the St. Lawrence west of Montreal. It is 790 mi (1,271 km) long and forms innumerable lakes. Explored by Samuel de Champlain in 1613, it became a major route for explorers, fur traders, and missionaries to the Great Lakes. In the 19th century the Rideau Canal was completed, linking Ottawa to Lake Ontario, and lumbering became important. It is now a source of hydroelectric power.