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 The lake bed is now a sandy and clayey plain. It is also a source for reed-sedge peat, which is harvested, processed, and packaged for agricultural applications; it enables plants to fix nitrogen and thereby reduces the need for fertilizer. The company harvesting the peat and the University of Minnesota-Duluth are developing processes to use the peat to extract mercury and other heavy metals, and also to remove sulfates from water by a method which enables the peat to be reused. Glacial Lake Duluth is the name given to the largest of a series of named lakes or lake stages