The Great Lakes region is one of the busiest shipping routes in North America. Vessels travel from Lake Superior to Lake Ontario, sometimes navigating the Great Lakes-St. Lawrence Seaway system and on to the Atlantic Ocean.
In Lake Superior, the Port of Thunder Bay is the westernmost Canadian port. The Port of Duluth-Superior (Duluth, Minnesota, and Superior, Wisconsin) is the westernmost U.S. port.
The Chicago Area Waterway System (CAWS) provides a navigation route for vessels between the Great Lakes Waterway and the Mississippi River system. The T. J. O’Brien Lock located along the Calumet River provides commercial access from CAWS to Lake Michigan. Nearly all commercial traffic on the CAWS consists of barges and tugs.
Lake carriers, also known as lakers, are a common sight on the Great Lakes. These massive ships transport taconite (iron ore pellets), cement, aggregates, and other commodities throughout the region
Depending on size, vessels may be limited to the Great Lakes or capable of reaching the Atlantic via the Great Lakes – St. Lawrence Seaway.
Locks on the St. Lawrence and on the Welland Canal are 766 ft (233.5 m) long, 80 ft (24.4 m) wide, and 30 ft (9.14 m) deep. The maximum allowed vessel size is slightly smaller: 740 ft (225.6 m) long, 78 ft (23.8 m) wide, and 26.5 ft (8.1 m) deep.
Since the opening of the Great Lakes – St. Lawrence Seaway, many vessels intended for the Great Lakes were built to the maximum size permissible by the locks. They are usually categorized as Seawaymax or Seaway-Max. Larger lake freighters cannot travel downstream beyond the Welland Canal.
Above the Welland Canal, ships are constrained only by the largest lock on the Great Lakes Waterway, the Poe Lock at the Soo Locks (at Sault Ste. Marie), which is 1,200 ft (365.8 m) long, 110 ft (33.5 m) wide and 32 ft (9.8 m) deep.
Ship enthusiasts enjoy ship spotting from locks, rivers, channels, harbors, and other points throughout the Great Lakes region.