The Keystone Corridor is a 349-mile (562 km) railroad corridor between Philadelphia and Pittsburgh, Pennsylvania, that consists of two rail lines: Amtrak and SEPTA's Philadelphia-to-Harrisburg main line, which hosts SEPTA's Paoli/Thorndale Line commuter rail service, and Amtrak's Keystone and Pennsylvanian inter-city trains; and the Norfolk Southern Pittsburgh Line. The corridor was originally the Main Line of the Pennsylvania Railroad. Since 2006, the line has been one of the high-speed corridors designated by the Federal Railroad Administration (FRA). The 24-mile section of track from Lancaster to Parkesburg permits trains of up to , while the 19-mile section between Paoli and Philadelphia allows up to . Amtrak runs two intercity rail services along the Keystone Corridor: the Harrisburg-to-New York City Keystone Service and the Pittsburgh-to-New York City Pennsylvanian. SEPTA operates daily Paoli/Thorndale commuter rail service between Philadelphia and Thorndale on the Philadelphia-to-Harrisburg main line. The towns along this stretch form a socio-cultural region called the "Philadelphia Main Line". The tracks from Pittsburgh to Harrisburg are owned and maintained by Norfolk Southern, which acquired them from Conrail. They include the Horseshoe Curve west of Altoona. The tracks between Harrisburg and Philadelphia are owned and maintained by Amtrak, and are the only part of the Keystone Corridor that is electrified. The tracks join the Northeast Corridor at Zoo Interlocking near the Philadelphia Zoo and 30th Street Station. History The right-of-way that would become the Keystone Corridor was mainly laid by two railroads. The tracks east of Dillerville, just west of Lancaster, were originally the Philadelphia and Columbia Railroad, part of the state-owned Main Line of Public Works. From Lancaster west to Harrisburg, the tracks were laid by the Harrisburg, Portsmouth, Mount Joy and Lancaster Railroad. Except for minor realignments, today's Keystone Corridor runs along the same path. Both lines eventually became part of the Pennsylvania Railroad's (PRR) main line. In 1915, the PRR electrified the line from Philadelphia's Broad Street Station to Paoli, then the west end of commuter service. Electrification west of Paoli to Harrisburg came in the 1930s, after the PRR completed electrifying its New York-Washington, D.C. section (the present-day Northeast Corridor). The total cost of electrification topped $200 million, which was financed by government-supported loans from the Reconstruction Finance Corporation and the Public Works Administration. Passenger service remained unprofitable, returned to profitability during World War II, and then slumped again. The PRR overhauled much of the right-of-way in the 1950s, but