The Homestead Steel Works, which was purchased by U.S. Steel Works in the late 1800's, closed in 1986 and the land surrounding this derelict factory is now a National Historic Landmark. The blast furnaces (above) were constructed in 1907 and are all that remain of this massive structure.
During operation, this factory contained 450 buildings and produced 200 million tons of steel per year during its peak.
(Historic Photo: Http://Bit.Ly/ZXhZZS)