Carnegie Steel Company was a steel-producing company primarily created by Andrew Carnegie and several close associates to manage businesses at steel mills in the Pittsburgh, Pennsylvania area in the late 19th century. The company was formed in 1892 and was subsequently sold in 1901 in one of the largest business transactions of the early 20th century, to become the major component of U.S. Steel. The sale made Carnegie one of the richest men in history. Creation Carnegie began the construction of his first steel mill, the Edgar Thomson Steel Works, in 1872 at Braddock, Pennsylvania. The Thomson Steel Works began producing rails in 1874. By a combination of low wages, efficient technology infrastructure investment and an efficient organization, the mill produced cheap steel, which sold for a large profit in the growing markets of industrial development. Carnegie alone estimated that 40% was returned on the investment, i.e., a profit of $40,000 from a $100,000 investment in the mill. The profits made by the Edgar Thomson Steel Works were substantial enough to let Carnegie and his partners, including Henry Clay Frick, his cousin George Lauder, and Henry Phipps Jr., buy other nearby steel mills. These included the Homestead Steel Works, which Carnegie acquired in 1883. The presence of the Allegheny, Monongahela, and Ohio rivers provided transport for the heavy materials used in steel production. Each plant was near to or alongside a river. Carnegie agreed to Frick's subsequent proposal that the various plants and assets, including H. C. Frick & Company, be consolidated into a single company. This consolidation occurred on July 1, 1892, with the formation of the Carnegie Steel Company. Operations The company headquarters were located in the Carnegie Building, an early skyscraper in Downtown Pittsburgh. Built to show its use of steel in its construction, the building was fifteen stories high and was left uncovered for a full year. The Carnegie Building was demolished in 1952. It was later rebuilt as a memorial in 2012. Carnegie Steel made major technological innovations in the 1880s, especially the installation of the open hearth furnace system at Homestead in 1886. It now became possible to make steel suitable for structural beams and, with the advanced work of George Lauder in arms and armament, for armor plate for the US Navy and the militaries of other governments, which paid far higher prices for the premium product. In addition, the plant moved increasingly