The Little Saw Mill Run Railroad was a standard gauge

Standard gauge

The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...

 coal railroad in Allegheny County, Pennsylvania

Allegheny County, Pennsylvania

Allegheny County is a county in the southwestern part of the U.S. state of Pennsylvania. As of the 2010 census, the population was 1,223,348; making it the second most populous county in Pennsylvania, following Philadelphia County. The county seat is Pittsburgh...

. It was incorporated July 23, 1850, and opened in April 1853. Originally, it was owned by the Harmony Society

Harmony Society

The Harmony Society was a Christian theosophy and pietist society founded in Iptingen, Germany, in 1785. Due to religious persecution by the Lutheran Church and the government in Württemberg, the Harmony Society moved to the United States on October 7, 1803, initially purchasing of land in Butler...

, and ran from Temperanceville, Pennsylvania

West End (Pittsburgh)

West End Village is a neighborhood in Pittsburgh, Pennsylvania's west city area. It has a zip code of 15220, and has representation on Pittsburgh City Council by the council member for District 2 ....

 on the Ohio River

Ohio River

The Ohio River is the largest tributary, by volume, of the Mississippi River. At the confluence, the Ohio is even bigger than the Mississippi and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream...

 to Banksville, Pennsylvania, running parallel to Saw Mill Run

Saw Mill Run

Saw Mill Run is a tributary of the Ohio River in Pennsylvania. It is an urban stream, and lies entirely within Allegheny County, Pennsylvania. The stream enters the Ohio just downstream from the Forks of the Ohio in Pittsburgh, at a place originally founded as the town of Temperanceville in the...

 and Little Saw Mill Run. In an agreement with the Pittsburgh Southern Railroad, it ran dual gauge

Dual gauge

A dual-gauge or mixed-gauge railway has railway track that allows trains of different gauges to use the same track. Generally, a dual-gauge railway consists of three rails, rather than the standard two rails. The two outer rails give the wider gauge, while one of the outer rails and the inner rail...

 tracks. It became part of the railroad empire of George J. Gould, merging with the West Side Belt Railroad

West Side Belt Railroad

The West Side Belt Railroad was a standard gauge railroad incorporated July 25, 1895. It ran from Temperanceville, to Clairton, Pennsylvania, with a branch to Banksville. It acquired the Little Saw Mill Run Railroad by merger in 1897, and the Bruce and Clairton Railroad in 1901. The railroad was...

in 1897.