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Schematic map of railroad lines pasing through ZOO junction in Philadelphia. (Click to enlarge.)

Zoo Junction (also known as Zoo Interlocking or just ZOO[A] is an important railroad junction in Philadelphia, Pennsylvania where the Amtrak Northeast Corridor meets the Keystone Corridor (formerly the Pennsylvania Railroad Main Line. It is so named because it is adjacent to the Philadelphia Zoological Garden. During the latter part of the 20th century, ZOO was among the largest and most complex junctions in the U.S.[1] Changes in the late 1990s simplified operations at ZOO, but it remains "the busiest and most famous rail junction in the United States,"[2] handling hundreds of long distance and regional commuter train movements every day.[3]


The Pennsylvania Railroad (PRR) completed development of its Main Line between Philadelphia and Pittsburgh in 1857, while the railroad was still assembling the pieces of what would eventually become the Northeast Corridor between New York City, Philadelphia and Washington. As part of its expansion toward New York, the PRR acquired the Philadelphia and Trenton Railroad (P&T), which owned tracks running from Trenton to the Kensington area in northeast Philadelphia. To extend the P&T line to Broad Street Station, where it could connect with the Main Line, would require buying and razing a long stretch of property running through the heart of the city – a prospect that would have been enormously expensive and politically controversial. Instead, the PRR built what became known as the Connecting Railway, which connected with the P&T at Frankford Junction and ran west across the Schuylkill River before turning south again to join the Main Line at what was then called Mantua Junction.[1][4] The Connecting Railway went into service in 1867, and by 1871 the PRR had acquired track rights through to Jersey City, just across the Hudson from New York.[B]

The Pennsylvania Railroad now had the capacity to run trains from the New York area all the way to Pittsburgh via the Connecting Railway. Since the route bypassed Broad Street Station, in 1884 a station was built at the Connecting Railroad's intersection with North Broad Street to provide service to Philadelphia. This station was initially called Germantown Junction; it was renamed North Philadelphia Station in 1915 after having been enlarged in several stages.[4]


  1. ^ By convention, names of railroad junctions and signal towers are spelled using all caps.
  2. ^ At first, PRR passengers had to use ferry services to reach New York City, since access to Grand Central Station was tightly controlled by the New York Central Railroad. Only in 1910, when the PRR opened Pennsylvania Station, which had its own tunnels beneath the Hudson, could passengers ride PRR trains all the way to the heart of Manhatten.[4]


  1. ^ a b Brotzman, Mike. "ZOO: Pennsylvania Railroad". The Signal Box. Retrieved 20 September 2014. 
  2. ^ Kyriakodis, Harry. "The other-other high line.". Hidden City Philadelphia. Retrieved 20 September 2014. 
  3. ^ Tawa, Steve. "SEPTA Says Adding Train Station To Philadelphia Zoo Is A Logistical Nightmare". CBS Philly. Retrieved 20 September 2014. 
  4. ^ a b c "Philadelphia – North Philadelphia, PA (PHN)". Great American Stations. Amtrak. Retrieved 15 November 2014. 

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