Northshore Mining Company is a wholly owned subsidiary of Cleveland-Cliffs who acquired Northshore in 1994. Cleveland-Cliffs subsidiaries also manage five other iron ore mines in Michigan, Minnesota and Eastern Canada. Northshore Mining was originally operated as Reserve Mining Company. It was the first taconite mining and processing facility in North America when it opened in 1955. The facility was reopened at reduced capacity in 1989 by Cyprus Minerals Company. Taconite is a hard, iron-bearing rock formed more than a billion years ago when the region was covered by a great sea. Minnesotas taconite belt, which varies from one to three miles wide and as much as 500 feet thick, extends northeastward from the Grand Rapids area up to Babbitt, where the mine that feeds the Silver Bay processing operations is located.