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
Iron mining in the United States large size of the Lake Superior deposits, and the access to cheap Great Lakes water transportation, enabled iron mining on a massive scale, located far from the iron furnaces. The Lake Superior iron ores, however, are located far from coal deposits, and the greater tonnage of coal required in steelmaking favored the location of furnaces closer to the coal mines. Favorable locations for steelworks using Lake Superior ore included Great Lakes ports such as Chicago, Cleveland, and Gary, as well as cities close to coal and with good water transportation, such as Pittsburgh. Although Lake Superior provides cheap shipping most