Duluth, Minnesota four Catholic schools with coverage up to grades 6 or 8, two Protestant schools, two Montessori schools, and six other charter and private schools. Due to its proximity to the Great Lakes, Duluth is the location for the Large Lakes Observatory. The Large Lakes Observatory operates the largest university-owned research vessel in the Great Lakes, the R/V Blue Heron. Built in 1985 for fishing on the Grand Banks, the Blue Heron was purchased by the University of Minnesota in 1997, sailed from Portland, Maine, up the St. Lawrence Seaway to Duluth, and converted into a limnological research vessel during the
Lake Superior adventurers. Lake Superior has been an important link in the Great Lakes Waterway, providing a route for the transportation of iron ore as well as grain and other mined and manufactured materials. Large cargo vessels called lake freighters, as well as smaller ocean-going freighters, transport these commodities across Lake Superior. Because of ice, the Lake is closed to shipping from mid-January to late March. Exact dates for the shipping season vary each year, depending on weather conditions that form and break the ice. The southern shore of Lake Superior between Grand Marais, Michigan, and Whitefish Point is known as the