This line started out as the Little Saw Mill Run Railroad in 1853. It connected with the Pittsburgh & Lake Erie Railroad yards at West End, PA, and headed east to a connection with the Pittsburgh Southern Railroad near Mount Washington. The LSMRRR merged with the West Side Belt Railroad in 1897, who extended the line further eastward; the WSBRR also started building from West Belt Junction to points west. This east-to-west line eventually became the mainline of the Pittsburgh and West Virginia Railroad, who purchased the WSBRR in 1932. The P&WV continued operating the original line from West Belt Junction to West End as their West End Branch.
The West End Branch was abandoned in 2011.