Atglen and Susquehanna Branch
The Atglen and Susquehanna (A&S) Branch was built by the Pennsylvania Railroad (PRR) between 1902 and 1906. The branch was built to relieve congestion on the Philadelphia to Harrisburg Main Line and the railroad's Columbia & Port Deposit (C&PD) line. It was designed for freight service, and minimizing the grade profile was of high importance, since freight service on the main line was hampered by relatively steep grade profiles. Thus the branch was often known simply as the "Low Grade."
During construction of the A&S Branch, the existing C&PD stone bridge at the Conestoga River washed out. Rather than rebuild, the C&PD bridge was combined with the A&S bridge to form a unique two-line, two-level steel viaduct known as the Safe Harbor Trestle. This bridge at the Conestoga carried the C&PD line over the river, while the A&S ran parallel and approximately 100 feet (30 m) above.
Construction was completed and the line opened for traffic by July 1906.
When combined with the railroad's Trenton Branch and Philadelphia & Thorndale Branch, the new line permitted the PRR to operate a low-grade bypass between Morrisville, Pennsylvania (just south of Trenton, New Jersey) and Harrisburg. This allowed freight trains to avoid the congestion of the eastern seaboard and the steep grades of the Main Line, 
The line flourished with freight traffic until the decline of northeast railroads and overall reduction in traffic made the line redundant. The line survived PRR's short-lived successor Penn Central (1968-76) until the era of Conrail (1976-89). Conrail downgraded the line, first removing the overhead catenary, then by rerouting traffic over the former Reading Company's line from Harrisburg to northern New Jersey. The last train on the line ran in 1988. Conrail petitioned the Interstate Commerce Commission to abandon the line in 1989 and track was removed around 1990.
Although trackage was dismantled prior to the 1999 breakup of Conrail by the Norfolk Southern Railway (NS) and CSX Transportation, the right-of-way had been retained due to disputes over the historical nature of the line's bridges, and passed to NS. A group called Friends of the Atglen-Susquehanna Trail had prepared to establish the line as a rail trail, but this plan was opposed by local township residents and ultimately failed. NS eventually sold the line to the seven townships through which it passes in July 2008. NS received $1 from each of the townships, although it also supplied the townships with a total of $1.4 million for bridge removal or repair.
Amtrak, which received ownership of PRR's electric traction system, continues to operate the two 138 kV transmission lines that run along the A&S right-of-way. The transmission lines, utilizing the distinctive PRR catenary poles, were replaced with typical utility-style monopoles in 2012.
The Pennsylvania Railroad catenary supports remain, operated by Amtrak under easement, to supply electricity from Safe Harbor Dam to the Parkesburg traction substation. Ironically, while they were one of the last parts of the line to be installed (c. 1938), they are the only remaining structure supporting railroad operations.
Since the right-of-way was transferred to the respective townships, about 13 miles (21 km) of the line has been opened to the public. Amtrak plans to upgrade the surface to a crushed-stone trail concurrently with its transmission line replacement project. The Safe Harbor ( ) and Martic Forge ( ) trestles remain closed.
- HAER PA-531, Data Pages, p. 3
- Except for a 10-mile (16 km) section between Thorndale and Parkesburg where freight and passenger traffic shared the four-track main line.
- Bart, Conestoga, Eden, Martic, Providence, Sadsbury, and West Sadsbury
- Amtrak, Chicago, IL (2010-04-28). "Amtrak is Working on the Railroad in 2010: $1 billion construction program funds projects to improve reliability, safety and security." Press release no. ATK-10-062.
- Traillink.com, April 2010
- "Pennsylvania Railroad, Safe Harbor Bridge, Spanning mouth of Conestoga River, Safe Harbor, Lancaster, PA ", Historic American Engineering Record, Library of Congress Call Number HAER PA,36-SAHAR,1-.
- Trail Planned for Former PRR Atglen & Susquehanna Branch (2005)
- Enola Low Grade Trail[dead link]
- AbandonedRails.com. "The Atglen and Susquehanna Branch"