River, southern Quebec.
It is 210 mi (338 km) long and flows north from Lake St. Lawrence River at Sorel. Explored in 1609 by Samuel de Champlain , it was used by the warring French and English colonists and later by commercial loggers and fishermen. A canal enables shallow-draft vessels to navigate between {{link=Montreal">Montreal and New York City via the St. Lawrence and Richelieu rivers, Lake Champlain, and the Hudson River .