Characteristics of the Duluth-Superior Harbor and Lake Superior

The twin ports of Superior, Wisconsin and Duluth, Minnesota were founded at the head of the world's greatest continuous mass of freshwater. The Laurentian Great Lakes contain about 20% of the world's freshwater resources. Half of that water is contained in the largest and most pristine of these lakes - Lake Superior. The tremendous size and purity of this water body make it one of the world's unique aquatic ecosystems. In addition to this resource, the Superior-Duluth harbor is protected by the largest natural inland sand bar in the world. Minnesota and Wisconsin Points, with a com­ bined length of over 9 miles, serve to protect what has become one of the largest and busiest ports in the world. The estuary itself contains over 11,500 acres of water and is fed by many small tributaries and two major river systems, the Nemadji and the St. Louis. The St. Louis River is the largest U.S. tributary to Lake Superior (See Figure 1)