Monongahela Inclined Plane Company.

The oldest incline plane in Pittsburgh was incorporated under Pennsylvania law in 1867. The charter permitted the construction and operation of a passenger-carrying incline between West Carson Street and Mount Washington. Built partly under the specifications of the famed John Roebling, the company began operating in 1870. The incline was reconstructed of metal in 1882 to replace the original structure; a parallel plane was added in 1884 to facilitate the hauling of freight. The construction of the Liberty Tunnels and McArdle-Roadway so reduced freight receipts that the freight incline was closed in 1935. In an effort to increase passenger revenues, that plane was electrified the same year. In 1965, the company was purchased by the Port Authority of Allegheny County which has continued to operate the incline as a part of its system.