 The NS main line follows the Susquehanna River (with trackage rights for Canadian Pacific Railway (CPR)), and leaves the county by crossing the river on Shocks Mills Bridge near Marietta.NS also has trackage rights over the Keystone Corridor, to which it is connected by the "Royalton Branch", which runs north along the river from the main line at Marietta, and the "Columbia Branch", which runs from the Corridor at Dillerville to the main line at Columbia.Two other NS branches originate on the Corridor