Duluth is a port city in the U.S. state of Minnesota and the county seat of St. Louis County. The fourth largest city in Minnesota, Duluth had a total population of 86,918 in the 2000 census and 84,397 according to July 1, 2007 census estimates. The Duluth MSA had a population of 275,486 in 2000. At the westernmost point of the Great Lakes on the north shore of Lake Superior, Duluth is linked to the Atlantic Ocean 2,300 miles (3,700 km) away via the Great Lakes and Erie Canal/New York State Barge Canal or Saint Lawrence Seaway passages and is the Atlantic Ocean's westernmost deep-water port. Duluth forms a metropolitan area with Superior, Wisconsin. Called the Twin Ports, these two cities share the Duluth-Superior Harbor and together are the world's largest inland port and one of the most important ports on the Great Lakes, shipping coal, iron ore, and grain. As a tourist destination for the Midwest, Duluth features America's only all-freshwater aquarium, the Great Lakes Aquarium, the Aerial Lift Bridge which spans the short canal into Duluth's harbor, "Park Point", the world's longest freshwater sandbar, spanning 6 miles, and is a launching point for the North Shore. The city is named for Daniel Greysolon, Sieur du Lhut, the first known European explorer of the area. Currently, Duluth is working in conjunction with Superior, Wisconsin to bring Google Fiber internet to the Twin Ports.