Minnesota has four ports on Lake Superior whose combined transported tonnage in 2007 was 68 million net tons. Minnesota's taconite industry represents 61% (38.4 million net tons) of Minnesota's 2007 total tonnage transported on Lake Superior. Taconite is mined in north-eastern Minnesota and shipped mainly via the Great Lakes to steel mills in Ohio and Pennsylvania. Western coal as of 2005, is the leading commodity handled in the Duluth/Superior harbor at over 20 million net tons in 2007.Our lake ports also handle cement, steel products, minerals, salt and packaged goods. Most of the products transported, especially western coal, are on the rise in tonnage shipped from the Duluth/Superior ports. The U.S. Corps of Engineers operates three of the locks on the Great Lakes/St. Lawrence Seaway system and maintains a 29-foot deep navigational channel. The Canadian government operates 13 locks on this system.

Ships that operate only on the Great Lakes are called "Lakers." Some of these Lakers range in size to over 1000 feet long, 105 feet wide and have a carrying capacity of 69,000 net tons. Any ship or laker operating on the Great Lakes can load to no more than 26' 6" draft in normal conditions. Since 1999, the lake levels have been so low that they have forced the ships to reduce their cargoes by as much as 6,000 tons per trip. The result of this forces the cost of shipping to go up.