Leaving the greater Harrisburg / Enola area from the west bank of the Susquehanna, the PRR's York Haven Line drops down river toward Columbia, PA. This line was a key component of PRR president Alexander J. Cassatt’s plan to build a low-grade freight bypass diverting traffic off the mainline from the Philadelphia area. Existing lines and new construction in the early 1900’s provided access to Baltimore by way of both the Northern Central via York and the Columbia and Port Deposit Branch via mainline connection at Perryville, Philadelphia via the new Atglen & Susquehanna and Lancaster via the original Philadelphia & Columbia. Running a distance of 15 miles east from Enola Yard along the former Northern Central alignment, this “branch” was actually one of the busiest electrified freight arteries in the east. Alongside the Susquehanna River in the town of Cly, the railroad maintained an interlocking here connecting the York Haven Line to the Northern Central. These lines would run parallel to Wago Junco where the NC drops southwest toward the city of York.
Cly tower was constructed in 1906; one of the few PRR interlockings utilizing an Armstrong plant of mechanical levers to control switches over the later US&S electro-mechanical installations. Constructed of brick the two-story tower was a contrast to neighboring installations built in the late 1930’s like Cola to the east, which controlled long stretches of line utilizing a Centralized Traffic Control installation. Though an important junction the Northern Central to York was never a preferred freight route in later days of the PRR hosting passenger trains and local freight. During the Penn Central years the route suffered heavy damage as a result of Hurricane Agnes. In a dire financial situation, Penn Central opted not to rebuild the route and Cly’s importance as an interlocking diminished resulting in the eventual closing of the tower in the early 1980’s under Conrail. Today there is little left here as Norfolk Southern works to modernize this line, the catenary poles have been cut down and position light signals replaced with modern installations. While connection is still made to the branch to York in a simplified interlocking at Wago the modern Cly is a mere curve and grade crossing at milepost 54 of the Enola Branch.