The Superior Entry is the only natural opening through the longest fresh water sandbar in the world. Sand deposits from the lake and the rivers created the bar, forming the harbor about 3000 years ago. First charted in 1861, the Entry was 1500 feet wide and 4 to 16 feet deep. The U.S. Corps of Engineers completed the present 1500 to 2000 foot long concrete piers in 1909 and now maintains a channel 500 feet wide and 32 feet deep, where currents sometimes reach speeds of more than 3 mph. The first ore shipped from the Mesabi Iron Range passed through the Entry in 1893. Today it serves one of the busiest ports in the United States, the western terminus of the St. Lawrence Seaway, handling cargoes of iron ore, coal, petroleum, and grain destined for ports throughout the world.
