The Tilden pit mine in Ishpeming was being worked by 1930. The Tilden open pit operations started by the Cleveland-Cliffs Iron Company in the early 1970s produced iron ore for pellets. Cleveland-Cliffs Iron Company was formed with the merger of two major iron mining companies on Michigan's Marquette Range in 1891. The Company had a number of mines operating in the Upper Peninsula by the outbreak of World War I. By the 1940s the high grade iron ores mined underground were becoming depleted. The Company developed a process to concentrate low grade ores into iron ore pellets in the 1950s, and C.C.I.C.'s last underground iron mine closed in 1979.
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