You know that rivers played a big part in America’s history. Explorers like Lewis and Clark followed the Missouri, Columbia, Snake, and other rivers westward. Barges moved goods and passengers up and down the Mississippi. Rivers are like highways. But did you ever think of lakes as part of America’s watery road map? All five Great Lakes are naturally connected. But it took some engineering to make those connections work for shipping. Today, this Great Lakes waterway connects the heartland of America to the North Atlantic Ocean and the Gulf of Mexico.

Like cars on a two lane road, upbound ships (away from the ocean) and downbound ships (toward the ocean) stick to shipping lanes and marked channels that are deep enough and safe for their vessels.

Great Great Lakes Facts

• The Great Lakes hold 20 percent of the world's fresh water.

• Ships carry 125 million tons of cargo over the Great Lakes each year. It is estimated that 6,000 ships have sunk in these waters.

• Together, the Great Lakes and the St. Lawrence Seaway make up the biggest water transportation route in the world.

• From Duluth, Minnesota, to the North Atlantic Ocean, a ship takes about nine days to travel 2,030 miles.

• There are 50 ports along the Great Lakes waterway.

• Four thousand ships use the St. Lawrence Seaway every year.

• $7 billion worth of cargo is shipped through the Great Lakes every year—iron ore, coal, bentonite clay, and manufactured goods.

• A ship can move one ton of cargo 500 miles on one gallon of fuel.

• A “saltie” is an ocean-going freighter that enters the Great Lakes. These 1,000-foot ships can carry the same load as 700 train cars or 2,800 large trucks.