Since the mines are located near the Great Lakes, the majority of the pellets are transported by rail to loading ports for shipments via vessel to steelmakers in North America.

[3] It also operates three coke-making facilities in Burns Harbor, Indiana, Monessen, Pennsylvania, and Warren, Ohio, with an annual capacity of 2.6 million tons, as well as a coal mine in Princeton, West Virginia.

[3] The company operates many fully-integrated steel mills and finishing facilities in Kentucky, Indiana, Illinois, Ohio, Michigan, Pennsylvania, West Virginia, and North Carolina.

[4][5] Samuel Mather and six Ohio-based associates had learned of rich iron-ore deposits recently discovered in the highlands of the Upper Peninsula of Michigan.

[6] Technological improvements, such as the Bessemer process, made it possible for mills in the North American Great Lakes region to produce steel on an industrial scale.

The south shore of Lake Erie was near a supply of coal, making that region an efficient point for the construction of steel mills.

[9] William G. Mather, the son of Samuel, guided Cleveland-Cliffs as president and later as chairman of the board from 1890 to 1947, participating in the transition from the hard-rock iron ore of Upper Michigan to the soft hematite of Minnesota's Mesabi Range and adjacent lodes.

In 1933, Edward B. Greene (the son-in-law of Jeptha Homer Wade II) replaced William G. Mather as the head of the company.

In 1950, the company celebrated its 100th anniversary with the publication of a commemorative book, A Century of Iron Men, by Harlan Hatcher, VP of the Ohio State University.

[19] As the Cold War continued, reserves of mineable hematite dwindled in northern Minnesota and Cleveland-Cliffs returned some of its focus to its traditional areas of interest around the Marquette Iron Range, where new deposits of magnetite were opened.

[20] In 1970, a high-grade iron-ore mine was opened at Pannawonica in the Pilbara region of Western Australia, with a 200 km (120 mi) rail line to processing facilities at Cape Lambert for which the residential township of Wickham was built.

Over half of the Marquette Iron Range employees were laid off and, in 1984, Cliffs withdrew from the Great Lakes shipping industry.

[20] In 2003, the company, in a joint venture with Laiwu Steel, purchased the assets of bankrupt Eveleth Mines and formed United Taconite LLC.

[28] In 2008, the company agreed to acquire Alpha Natural Resources but called off the transaction in November 2008 due to the financial crisis of 2007–2008.

[39] The reconstituted Board moved to shift the company's strategic objectives from global diversification to a renewed focus on strengthening its U.S. iron ore business.

[40] Cliffs announced plans in early 2016 to close the Empire Mine near Marquette, Michigan, terminating the jobs of approximately 400 workers.

[45][46][47] In December 2020, the company acquired the United States operations of ArcelorMittal for approximately $1.4 billion, making it the largest producer of flat-rolled steel and iron ore pellets in North America.

[48][49][50] In February 2022, Cleveland-Cliffs agreed to pay a $3 million settlement related to Clean Water Act violations, including a cyanide and ammonia spill in August 2019 that killed thousands of fish and closed Lake Michigan beaches.

[51] On July 28, 2023, Cleveland-Cliffs executives sent a proposal to U.S. Steel CEO David Burritt, to acquire the company for a total enterprise value of $10 billion, in a cash and stock deal.

The companies also sued CEO Goncalves and United Steelworkers president Dave McCall, charging “anticompetitive and racketeering activities illegally designed to prevent any party other than Cliffs from acquiring US Steel as part of an illegal campaign to monopolize critical domestic steel markets”.

"[58][59] On July 15, 2024, Cleveland-Cliffs announced that it would acquire Stelco, a Canadian steel manufacturer, for $2.5 billion in cash and stock.