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.

St. Louis County is a county located in the Arrowhead Region of the U.S. state of Minnesota. As of the 2020 census, the population was 200,231. Its county seat is Duluth. It is the largest county in Minnesota by land area, and the largest in the United States by total area east of the Mississippi River. St. Louis County is included in the Duluth, MN–Superior, WI Metropolitan Statistical Area.