ALLETE’s headquarters in Duluth, Minn. overlooks the western end of Lake Superior, the cleanest, clearest, deepest and coldest of the Great Lakes. It is the largest freshwater lake in the world by surface area, and the third largest by volume. Lake Superior is connected to the Atlantic Ocean by the St. Lawrence Seaway. The 2,343 mile trip by boat from the Duluth, Minn./Superior, Wis. port to the ocean takes about seven days. It’s the busiest inland port in the country, with more than 1,000 vessels visiting each year. Because of its great size, Superior has a 191-year retention time, a measure of how long water stays in the lake based on volume and the mean rate of outflow. Lake Superior contains three quadrillion (3,000,000,000,000,000) gallons of water. That's ten percent of the world's fresh surface water.