Great Lakes Waterway River between Huron and Erie. Usually, one or more U.S. Coast Guard icebreakers help keep the water passage open for part of the fall and early winter, although shipping usually ceases for two to three months thereafter. The Great Lakes Waterway is co-administered by the governments of Canada and the United States of America. The waterway allows passage from the Atlantic Ocean to the inland port of Duluth on Lake Superior, a distance of and to Chicago, on Lake Michigan, at . Together with the Saint Lawrence Seaway, the Waterway allows both ocean-going vessels and the ore, grain and coal-bearing
Proglacial lakes of Minnesota occupying parts of the Lake Superior basin. As its current outlet to the east was blocked by the Superior Lobe of the ice sheet, Lake Duluth drained through two outlets which crossed the present Laurentian Divide to the valley of the Saint Croix River and the Mississippi. One outlet was a route from the western part of the lake through the Nemadji River basin and down the present Moose and Kettle Rivers; the other was via the modern Bois Brule River to the Saint Croix. At its peak, Lake Duluth was 148 meters higher than Superior's present level. When the