Duluth, Minnesota Lakes Waterway and the Saint Lawrence Seaway. Duluth forms a metropolitan area with neighboring Superior, Wisconsin, called the Twin Ports. The cities share the Duluth–Superior harbor and together are the Great Lakes' largest port, transporting coal, iron ore (taconite), and grain. A tourist destination for the Midwest, Duluth features the United States' only all-freshwater aquarium, the Great Lakes Aquarium; the Aerial Lift Bridge, which spans the Duluth Ship Canal into the Duluth–Superior Harbor; and Minnesota Point (known locally as Park Point), the world's longest freshwater baymouth bar, spanning . The city is also the starting point for vehicle trips along
Transportation in Minnesota rivers. Commercial water transportation now is limited to the shipment of bulk commodities on two routes. Barges haul grain and other products down the Mississippi River system from the ports of Minneapolis (the head of navigation), St. Paul, Red Wing and Winona on the Mississippi, and Savage (on the Minnesota River), to downstream river ports, and to ports on the Gulf of Mexico for transshipment to ocean-going cargo ships. Cargo vessels known as lakers haul grain, coal, and iron ore from the Lake Superior ports of Duluth, Superior, Two Harbors, and Silver Bay, through Lake Superior to the lower Great