Pittsburgh Southern Railway

Pittsburgh Southern Railway

Locale	Pennsylvania, U.S.
Dates of operation	1876–1884
Predecessor	Pittsburgh, Castle Shannon and Washington Railroad, Pittsburgh Railroad, Washington Railroad
Successor	Baltimore and Ohio Short Line Railroad
Track gauge	4 ft 8 1⁄2 in (1,435 mm) standard gauge
Previous gauge	3 ft (914 mm) gauge
Length	37 miles (60 km)

The Pittsburgh Southern Railway was a railroad in the U.S. state of Pennsylvania. It was formed in March 1879 by the merger of the 3 ft (914 mm) narrow gauge Pittsburgh Southern Railroad (which was the 3 ft 4 in (1,016 mm) narrow gauge Pittsburgh, Castle Shannon and Washington Railroad from July 1877 to April 1878), Pittsburgh Railroad, and Washington Railroad. It ran from Washington to Castle Shannon, where it connected to the Pittsburgh and Castle Shannon Railroad. An attempt to use the 4 ft 8 ¹⁄₂ in (1,435 mm) standard gauge Little Saw Mill Run Railroad as a substitute connection to Pittsburgh using dual gauge track led to the Castle Shannon Railroad War of 1878.

It was converted to 4 ft 8 ¹⁄₂ in (1,435 mm) standard gauge in 1883, purchased by the Baltimore and Ohio Railroad on November 20, 1884 and reorganized as the Baltimore & Ohio Short Line Railroad.