It was decided to have a portion of the line be constructed on an elevated structure due to the higher cost of building subways in the Bronx, whose soil was irregular and rocky.
As part of Contract 3 of the agreement, between New York City and the IRT, the original subway opened by the IRT in 1904 to City Hall, was to be extended north from Grand Central along Lexington Avenue into the Bronx, with a branch running northeast via 138th Street, Southern Boulevard and Westchester Avenue to Pelham Bay Park.
As part of the construction of this section of the line, a new bridge would be built over the Bronx River, which would be 61 feet (19 m) above high tide.
[23] Express service did not start until this date because of the increase in ridership from the huge Parkchester housing complex at East 177th Street.
With the additional space, it would no longer be required to lay up trains on the middle track of the line between East 177th Street and Pelham Bay Park, and it would allow for full day express service.
[31] The IRT Pelham Line would be very easily converted to B Division standards, and connected to the Second Avenue Subway as Route 132–B of the 1968 Program for Action.
[32] The Brook Avenue station just east of Third Avenue–138th Street on the IRT Pelham Line would be reconstructed to allow a cross-platform interchange.
[35] Under Phase 2 of the Program for Action, the Pelham Line would have been extended to a modern terminal in the Co-op City housing complex.
Expected to be completed by the mid-1970s and early 1980s,[36][37] lines for the Program for Action had to be reduced or canceled altogether due to the 1970s fiscal crisis.
<6> trains make all stops north of Parkchester, then run express using the center track between that station and Third Avenue–138th Street in the peak direction.
[2] Beginning at a junction with the IRT Jerome Avenue Line north of the Lexington Avenue Tunnel at 135th Street,[12] the IRT Pelham Line runs beneath 138th Street for the first three stations in Mott Haven, then curves to the northeast along eastbound Bruckner Boulevard before shortly curving north again along Southern Boulevard.
After 145th Street at Samuel Gompers High School, the line curves to the northeast continuing to run under Southern Boulevard.
The line returns under eastbound Bruckner Boulevard again, only to leave at Whitlock Avenue and begins to emerge from underground at Aldus Street.
After the Westchester Yard the line runs over the Hutchinson River Parkway interchange just west of Middletown Road station.
After the release of the 1974 film adaptation, the New York City Transit Authority banned any schedule of a train leaving this station at 1:23 am or 1:23 pm.
Eventually this policy was rescinded, but due to the superstitions involved, dispatchers have continued to avoid scheduling a Manhattan-bound train to leave at 1:23.