Commonwealth Steel Company was an American steel company based in Granite City, Illinois and founded in 1901 "by some of the young men who had helped establish the American Steel Foundry". The company produced steel castings and railroad supplies at its 10-acre (4 ha) plant, employing about 1,500 people.
Over the years, the company's 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. The significance of the company to the rail industry became evident when two locomotive manufacturers, and customers of Commonwealth, Baldwin Locomotive Company and American Locomotive Company, formed General Steel Castings Corporation in 1928 and acquired Commonwealth and its products in 1929.
Clarence H. Howard, who controlled the Double Body Bolster Company, received orders for cast-steel bolsters for railroad passenger cars to be used in an exhibit at the upcoming 1904 St. Louis World's Fair but his company was unable to produce bolsters of the specified size. Cast steel bolsters of that size had not been previously manufactured. Mr. Howard negotiated with the Commonwealth Steel Company to produce the new steel bolsters and he assisted during the production process. Clarence H. Howard, along with his former schoolmates, H. M. Pflager, and G. K. Hoblitzelle assumed control of Commonwealth in 1904. Mr. Howard would head the company for 23 years and retire in April 1931, two years after Commonwealth merged with General Steel Castings Corporation and only months before his death in December 1931.
The company was supportive of Americanization (helping foreigners adapt to the American way of life) efforts at Lincoln Place, providing free English-language classes to foreign-speaking immigrants, and was strongly in favor of Prohibition. An article in the December 1915 issue of The Commonwealther was titled "A saloon is sometimes called a bar - and so it is!" The company also encouraged fellowship and the Golden Rule through the Fellowship Club.
The company established the Commonwealth School in 1906 to serve the educational needs of "Commonwealthers." Apprentices would be given up to four hours a week, on company time, to study mathematics, mechanical drawing, and blue print reading.