The Great Lakes and the St. Lawrence Seaway

The five Great Lakes — Superior, Michigan, Huron, Erie, and Ontario — form the largest group of freshwater lakes on Earth by combined surface area, covering roughly 244,000 square kilometers and holding, according to U.S. Environmental Protection Agency and Environment Canada estimates, about 21 percent of the world's surface fresh water. Four of the five lakes straddle the U.S.-Canada border; Lake Michigan alone lies entirely within the United States. Together they form a single interconnected system draining eastward, ultimately reaching the Atlantic Ocean via the St. Lawrence River.