Edgar Thomson Steel Works

The Edgar Thomson Steel Works is a steel mill in the Pittsburgh area communities of Braddock and North Braddock, Pennsylvania, United States. It has been active since 1872. It is currently owned by U.S. Steel and is known as Mon Valley Works – Edgar Thomson Plant on its official website.

The mill occupies the historic site of Braddock's Field, on the banks of the Monongahela River east of Pittsburgh. On July 9, 1755, in the Battle of the Monongahela, French and Indian forces from Fort Duquesne defeated the expedition of British General Edward Braddock, who himself was mortally wounded.

Braddock's Field also was the site of a rally of rebellious militiamen and farmers during the Whiskey Rebellion, prior to a massive march on the town of Pittsburgh on August 1, 1794.

The site is on the banks of the Monongahela, which provides cost-effective, riverine transportation of coke, iron and finished steel products.

The Edgar Thomson Steel Works was designed and built because of the Bessemer process, the first inexpensive industrial process for the mass production of steel. In the process, air blowing through the molten iron removed impurities via oxidation. This took place in the Bessemer converter, a large ovoid steel container lined with clay or dolomite.

In the summer of 1872, while in Europe, Andrew Carnegie learned about the Bessemer process. He returned to Pittsburgh with plans to build his own Bessemer plant. Some of the partners, stockholders, and connected people were William Coleman, Andrew Kloman, Henry Phipps, David McCandless, Wm. P. Shinn, John Scott, David A. Stewart, James Robb Wilson and Thomas Carnegie. The firm was known as Carnegie, McCandless, and Company. The plant was named after J. Edgar Thomson, who was the president of the Pennsylvania Railroad.Carnegie Brothers and Company was created by the consolidation of the steel businesses owned by Andrew Carnegie in the early 1880s. Those steel and coke works that were consolidated were:

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