Mountain Iron is a city in Saint Louis County, Minnesota, United States, in the heart of the Mesabi Range. The population was 2,878 at the 2020 census. U.S. Highway 169 serves as a main route in Mountain Iron. The city's motto is "Taconite Capital of the World". The local mine, Minntac, is owned by the United States Steel Corporation. Mountain Iron is part of the Quad Cities, with Virginia, Eveleth, and Gilbert.