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
Lake Superior National Estuarine Research Reserve freshwater estuaries. One of these estuaries formed where the waters of the St. Louis River enter Lake Superior. Lake Superior, which is bordered by Michigan, Minnesota, Wisconsin and Ontario, Canada, is the largest of the Great Lakes and the most pristine. Freshwater estuaries occur where rivers and Great Lakes water mix in shallow wetlands located near the mouth of a river. The Reserve contains all three common defining characteristics of a Great Lakes freshwater estuary including a) presence of a drowned river mouth b) adequate zone of transition between lake and river water and c) influence from tide or seiche.