Lake Superior was discovered in 1629 by the French explorer Brule. It is the largest expanse of fresh water in the world, and its water is chemically pure. Its area is 31,800 square miles, with 1,500 miles of coast; its greatest length is 350 miles, its greatest breadth 160 miles, its greatest depth 1,333 feet, and its surface 602 feet above sea level, about 21 feet above Lake Huron. The first steamer on Lake Superior was the Independence in 1845. The Independence came from Chicago, and because there was no canal or locks at the Soo at that time, it had to be portaged around the Soo Rapids. The freighters passing this point carry more tonnage each season than the combined tonnage of the Panama, Kiel, and Suez canals.