Formed from the merger of the Federal Steel Company, Carnegie, American Sheet Steel Company, American Steel & Wire Company, American Tin Plate Company and the National Tube Company in 1901, US Steel produced 67% of US steel production in its first year of operation. The corporation began to heavily diversify into other industries in the 1980s and was re-organized as USX Corporation in 1986. US Steel separated from USX again in 2002 and has acquired steel-making assets in the United States, Europe and Canada. As of 2007 US Steel was the fifth largest steel manufacturer in the world.

http://www.ussteel.com/corp/company/profile/history.asp