The Twin Ports of Duluth, Minnesota and Superior, Wisconsin, are located at the western part of Lake Superior (the westernmost of North America's Great Lakes) and together are considered the largest freshwater port in the world. They are twin cities and seaports, connected to the Atlantic Ocean through the Great Lakes and the Saint Lawrence Seaway. The Twin Ports are at the core of the U.S. Census Bureau's "Duluth, MN-WI Metropolitan Statistical Area", which includes all of Wisconsin's Douglas County, and Minnesota's Carlton and Saint Louis counties. With a 2010 census population of 279,771, the Duluth MSA ranked as the 165th largest metropolitan area in the United States.
The area is home to two very long bridges: the Richard I. Bong Memorial Bridge (carrying U.S. Highway 2) and the John Blatnik Bridge (carrying I-535 and U.S. Highway 53). While their central spans are not notably lengthy, the overall lengths are very impressive, with each reaching across more than 1.5 miles (2.5 km) of water.
However, when visitors to the area come to see bridges, they pay much more attention to the historic Aerial Lift Bridge that serves as a gateway to the port. It must be raised and lowered whenever ships enter or exit the Duluth side of the harbor, though the natural inlet closer to Superior is not similarly obstructed.
Together, the cities rank as the 19th-busiest port in the country overall (44.2 million short tons [40.1 million tonnes] per year) as of 2002, though the area is the 7th-busiest port (13.8 million short tons [12.5 million tonnes] per year) when measured on foreign exports alone.