Twenty miles up the Monongahela River from Pittsburgh is the Clairton Works, the largest coke plant in the USA. It is part of the chain of U.S. Steel’s Mon Valley Works, supplying coke to the blast furnaces at the Edgar Thompson Plant. Coke is baked and processed coal, and is an important ingredient in steel. The plant produces 4.7 million tons of coke annually, selling much of it to other customers, like power plants and other steel mills.