The fourth-largest city in Minnesota, Duluth enjoys a strategic location upon the hillsides rising above Lake Superior, the largest freshwater lake in the world. Together with neighboring Superior , Wisconsin, Duluth is a major port for the transportation of agricultural products and ore from the nearby Iron Range of Northeastern Minnesota. The city grew rapidly during the late 1800's and early 1900's, with its population peaking in 1960 at almost 107,000. The winters are long and snowy, but the summers in the "Air-Conditioned City" are pleasant with cool lake breezes and many hours of sunshine. Buildings downtown are linked by a climate-controlled skyway system, the third-largest in the state, after those in downtown Minneapolis and St. Paul .