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
Lake Superior National Estuarine Research Reserve county, state, and university entities. The Reserve is sponsored by the Cooperative Extension division of University of Wisconsin-Extension and hosted at the University of Wisconsin-Superior. Reserve offices and research facilities are on Barker's Island in Superior Bay, part of the Duluth-Superior harbor. The Lake Superior Reserve site represents a previously unrepresented biogeographic region within the National Estuarine Research Reserve System – the Great Lakes, Lake Superior subregion. The Lake Superior Reserve and the Old Woman Creek (Lake Erie in Ohio) are the only Great Lakes freshwater estuaries in the Reserve System. This subregion contains all of Lake Superior and its