" The Monongahela Railroad was a joint venture of the Pennsylvania Railroad (PRR) and the Pittsburgh and Lake Erie Railroad (P&LE), both of which had plans to extend their lines in the area. Each company appointed four of their members to the board of directors, who held their first meeting in January 1901. The newly formed Monongahela Railroad acquired many lines in the area from the PV&C as well as the Southwest Pennsylvania Railway Company, as well as the 19 mile (30km) right of way from Brownsville to Adah from the PRR, for the sum of $519,696.13.

In 1905, the Dunlap Creek branch opened, which served several mines and coke works and also interchanged with the Baltimore and Ohio Railroad. The last move on this line was on November 6, 1975. The track was removed, and the real estate disposed.

In 1909, the 4.2 mi (7 km) Rush Run branch was constructed, and a patch town (Sarah, Pennsylvania) was constructed to house the workers at what would have been a coal mine. It was later determined, however, that the coal did not belong to the mine developer, and the line was abandoned, the town was scrapped. Only four trains ever ran on this line, those carrying the ballast to complete the track."