The Commonwealth Steel Company was an American steel company based in Granite City, Illinois, founded in 1901 "by some of the young men who had helped establish the American Steel Foundry".[1] The company produced steel castings and railroad supplies at its 10-acre (4-hectare) plant, employing about 1,500 people.[1]
Over the years, its innovative steel castings products made Commonwealth an increasingly important manufacturer and supplier to the rail industry. By 1928, "practically all locomotives and passenger cars built in the United States" were using Commonwealth products.[2] The significance of the company to the rail industry became evident when two locomotive manufacturers, and customers of Commonwealth, the Baldwin Locomotive Company and the American Locomotive Company, formed General Steel Castings Corporation in 1928 and incorporated Commonwealth and its products as the Commonwealth Steel Division.