Great Lakes Shipping
Great Lakes shipping is one of the foundations of the U.S. and North American economies. Each year vessels of all flags work the Great Lakes and load as much as 200 million tons of cargo at more than 100 ports.
The primary cargos moving on the Great Lakes are iron ore, coal, limestone and grain. Shipments of iron ore average about 60 million tons a year. Iron ore is the primary raw material required to make steel.
The coal trade averages about 42 million tons a year. Most coal moving on the Lakes is for power generation, but some coal is used in the steelmaking process.
Limestone cargos generally top 38 million tons a year. Aggregate is used by the construction industry as a base for highways and roads and in building homes, schools, hospitals, office buildings... Fluxstone is used as a purifying agent in the steelmaking process.
Grain cargos, most of which are exported overseas, total about 13 million tons a year. Vessels in the export trade usually bring specialty steels and heavy machinery to the Lakes.
Other cargos include salt to de-ice roads, cement and sand for the construction industry, and potash for fertilizers.
The U.S. and Canadian vessels that work the Great Lakes ("Lakers") are unique in that most are what are called "self-unloaders." The vessels are so equipped that they can discharge dry-bulk cargo without any assistance from shoreside personnel and equipment. Ocean-going vessels (salties) carrying general cargo are unloaded by longshoremen.
Winter in the Great Lakes region brings heavy ice to the Great Lakes, so the Lakes are mostly quiet from late January to early March. The locks at Sault Ste. Marie, Michigan (Soo Locks), open on March 25 and close the following January 15. The St. Lawrence Seaway opens in late March and generally closes by year's end. The Lakes still have significant ice covering them at the opening and closing of navigation, but commerce is able to move because the U.S. and Canadian Coast Guards have icebreakers stationed on the Lakes.
