Mountain Iron is a city in St. Louis County, Minnesota, in the heart of the Mesabi Range. As of the 2000 census, the city population was 2,999. U.S. Highway 169 serves as a main arterial route in the city. Minntac is owned by the United States Steel Corporation (U.S. Steel). Mountain Iron is part of the Quad Cities of Virginia, Eveleth, and Gilbert.