What) The Saint Lawrence (French: fleuve Saint-Laurent; Tuscarora: Kahnawáʼkye; Mohawk: Kaniatarowanenneh) is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage conveyor of the Great Lakes Basin.
The Saint Lawrence River originates at the outflow of Lake Ontario near Kingston, Ontario. From there, it passes Montréal, Trois-Rivières, and Québec City before draining into the Gulf of Saint Lawrence which is one of the largest estuaries in the world. The estuary portion begins just downstream from Québec City and the river becomes tidal in the vicinity of Québec City. The Saint Lawrence runs 3,058 km (1,900 mi) from the farthest headwater to the mouth and 1,197 km (743.8 mi) from the outflow of Lake Ontario. (1)
Where) It's impossible to miss.
Why) We had already seen all of the Great Lakes on our trip making it natural to see where they ended up.