Nemacolin is a census-designated place (CDP) in Greene County, Pennsylvania, United States founded as a company town around the workings of a Youngstown Sheet and Tube company owned and operated coal mine in 1917. The name reflects a noted Amerindian ally— Chief Nemacolin, who showed the Virginia and Pennsylvania settlers how to cross the successive Allegheny barrier ridges via the Cumberland Narrows and the Nemacolin Trail —which Braddock's Expedition widened into a wagon road through the barrier range.