the Philadelphia and Trenton Railroad, opened in 1867. It served as another connecting link, running from the Junction Railroad and PRR main line at Zoo interlocking east to the lines heading north from downtown. In 1871, the south end was reconfigured due to the Darby Improvement, which moved the PW&B to the current Northeast Corridor alignment; the old alignment was leased to the Reading in 1873. The Reading began operating passenger trains over the entire Junction Railroad on September 3, 1873, with a transfer to the PW&B at Grays Ferry. On April 1, 1876, the Reading leased the northern piece of the line for a year to access a temporary station for U.S. centennial celebrations. The PRR ownership of the middle portion led to problems starting in 1880, when the Baltimore and Ohio Railroad shifted its New York traffic coming off the PW&B to the Delaware and Bound Brook Railroad, using the entire Junction Railroad to Belmont. The PRR gained control of the PW&B in 1881, forcing the B&O to build the Baltimore and Philadelphia Railroad to retain Philadelphia access; this line completely avoided the Junction Railroad by running along the east bank of the Schuylkill. Through Reading trains were also moved off the Junction Railroad, using the B&O's route instead. The PB&W leased the Junction Railroad on March 1, 1899. The PRR's West Philadelphia Elevated line, completed in 1904, provided an alternate route for freight trains that would use the central piece of the Junction Railroad through the Market Street Tunnel or the PRR's River Line along the Schuylkill. Merged with PRR The Junction Railroad was merged into the PRR on March 31, 1908, becoming the Belmont Branch north of and the Grays Ferry Branch (also 32nd Street Branch) south of West Philadelphia. Except for the Market Street Tunnel, the Grays Ferry Branch was part of the main line from Broad Street Station towards Baltimore. The Belmont Branch remained a connection to the Reading. Post-PRR After the PRR and Reading both became part of Conrail in 1976, it became part of the Harrisburg Line, along with the West Philadelphia Elevated Branch and Delaware Extension to Greenwich Yard. In the 1999 breakup of Conrail, the Harrisburg Line south of Belmont became CSX Transportation's Harrisburg Subdivision. The old Junction Railroad through the Market Street Tunnel has been abandoned, and the rest of the line is now a SEPTA Regional Rail main