Cliffs Natural Resources, formerly Cleveland-Cliffs, is a Cleveland, Ohio company that specializes in the mining and processing of iron ore and the mining of coal. The firm is an independent company whose shares are traded on the New York Stock Exchange. The firm has stated that it had approximately 4,000 employees and a 28% share of the iron-ore pellet market.

In Marquette County, Cliffs currently operates the Tilden and Empire mines. It formerly operated a number of other properties, including the Mather A and Mather B mines in Negaunee, the Eagle Mills pellet plant in Negaunee Township, the Humboldt Mine, the Republic Mine, and the Pioneer Pellet Plant. 

The corporate history starts with the 1847 Cleveland Iron Mining Company, which was formed by Samuel Mather and his Ohio based associates. In 1890 the company merged with the Cliffs Iron Company and took the name Cleveland-Cliffs Iron Company. It kept that name throughout the 20th century, changing it to Cliffs Natural Resources in October 2008 after purchasing coal mining interests.

Wikipedia: Cliffs Natural Resources

Books: Iron Will: Cleveland-Cliffs and the Mining of Iron Ore, 1847-2006. By Terry S. Reynolds, Virginia P. Dawson, Wayne State Univerity Press