Duluth, Minnesota at the western end of the Saint Lawrence Seaway, the Duluth–Superior seaport is the largest and farthest-inland freshwater seaport in North America. By far the largest and busiest on the Great Lakes, the port handles an average of 46 million short tons of cargo and over 1,100 visits each year from domestic and international vessels. With of waterfront, it is one of the leading bulk cargo ports in North America and ranks among the top 20 ports in the United States. Duluth is a major shipping port for taconite pellets, made from concentrated low-grade iron ore and destined for midwestern
Duluth, Minnesota sandy core. As the last glacier retreated, meltwaters filled the lake to as high as 500 feet above the current level; the Skyline Parkway roughly follows one of the highest levels of the ancient Lake Superior, Glacial Lake Duluth. The sandstone that buried the igneous rocks of the rift is exposed near Fond du Lac. At one time a large number of quarries produced the stone, sold as Fond du Lac or Lake Superior brownstone. It was widely used in Duluth buildings and also shipped to Minneapolis, Chicago, and Milwaukee, where it was also used extensively. The weathered sandstone forms