ArcelorMittal employs more than 18,000 people in America, according to its website.
The deal includes more than 25 facilities, including mines, steelmaking facilities, and other operations.
ArcelorMittal is the largest steel manufacturer in North and South America, according to the company.
The $1.4 billion deal will make Cleveland-Cliffs the largest flat-rolled steel producer in North America, according to a press release.
The move also makes Cleveland-Cliffs the largest iron ore pellet producer in North America.
Cleveland-Cliffs was founded in 1847.
Cleveland-Cliffs also acquired AK Steel in March 2020.