Laurentian Divide

The Laurentian Divide (green) extends from Triple Divide Peak (Montana) to the coast of the Labrador Peninsula at the 60th parallel north, which is the northern limit of the Atlantic Ocean. The northern drainage divide which demarcates the Hudson Bay Watershed (blue) extends to the northern limit of the Hudson Strait.

The Laurentian Divide or Northern Divide is a continental divide dividing the direction of water flow in eastern and southern Canada and the northern Midwestern United States. Water north of the height of land flows to the Arctic Ocean by rivers to Hudson Bay or directly to the Arctic. Water south of the divide makes its way to the Atlantic Ocean by a variety of streams, including the Great Lakes and Saint Lawrence River to the east, and the Mississippi River to the Gulf of Mexico to the south. Some sources consider Hudson Bay to be part of the Atlantic Ocean, not the Arctic, which would make the Laurentian Divide a lesser divide between the seas of one ocean.

On the north and east, the divide's terminus is at Cape Chidley's Killiniq Island, on the Labrador Sea where that sea, part of the Atlantic Ocean, meets Hudson Strait, which connects to Hudson Bay in the Arctic Ocean. It cuts through eastern Canada, dips into the United States, and re-enters Canada before terminating in the Rocky Mountains in the western United States.

On Killiniq Island, the divide forms the boundary between Labrador and Nunavut, then a good portion of the Labrador-Quebec border. It turns west to cross central Quebec and Ontario; it marks the original northern boundary that both provinces held at the time of Confederation in 1867, although both have since expanded significantly northward. Waters east and south of the divide flow into the Labrador Sea, the Gulf of St. Lawrence, or the Saint Lawrence River and the Great Lakes which are drained by that river.

Marker sign for the Divide along Highway 101 in Ontario.

The divide crosses into the United States in northeast Minnesota at the Height of Land Portage. Near Hibbing it forms a three-way divide at the Hill of Three Waters (47.47184°N 92.96549°W / 47.47184; -92.96549) where the watersheds of the St. Lawrence and the Mississippi River systems meet with the Hudson Bay basin. It crosses to the extreme northeast corner of South Dakota and passes through North Dakota to that state's northwestern corner. The U.S. sections of the divide separate the watersheds of the Rainy River and Red River of the North from the basins of the Mississippi and Missouri Rivers. The divide formed the northern boundary of the United States' Louisiana Purchase.

The divide crosses the southern parts of Saskatchewan and Alberta before dropping back into the United States where it meets the Great Divide at Triple Divide Peak in Glacier National Park in Montana. The Laurentian Divide's western terminus is here, but the watershed boundaries continue. The Arctic watershed's limit follows the Great Divide running north, forming part of the Alberta-B.C. border, entering the interiors of B.C. and Yukon, forming two segments of the Yukon-Northwest Territories border, eventually crossing into northern Alaska, through to that state's Lisburne Peninsula and the sea.

External links

• U.S. Geological Survey Geographic Names Information System: Laurentian Divide (Minnesota portion)