The Saint Lawrence River is a large river in the middle latitudes of North America, flowing from Lake Ontario into the Gulf of Saint Lawrence, the largest estuary in the world. It connects the Great Lakes to the Atlantic Ocean and forms part of the international boundary between Ontario, Canada, and New York, USA. The river is the primary drainage outflow of the Great Lakes Basin. In the 1950s, the Saint Lawrence Seaway was constructed, a system of locks, canals, and channels that permits ocean-going vessels to travel all the way to Lake Superior. This made the river one of the most important commercial waterways in the world. Ecologically, the river's estuary is famous for its population of Beluga whales, though they are currently listed as an endangered species due to pollution and noise from shipping traffic.