Operation of the first subway began on October 27, 1904, with the opening of the original 28 stations of the New York City Subway from City Hall to 145th Street on the West Side Branch including the 125th Street station. In 1948, platforms on the IRT Broadway–Seventh Avenue Line from 103rd Street to 238th Street were lengthened to to allow full ten-car express trains to stop at this station. Previously, the station could only hold six-car local trains. The platform extensions were opened in stages. The platform extensions at 125th Street opened on June 11, 1948. In 2002, it was announced that 125th Street would be one of ten subway stations citywide, as well as one of five on the IRT Broadway–Seventh Avenue Line, to receive renovations. The renovation took place the following year.
Station layout
This station was part of the original subway. It has two side platforms and three tracks; the center track is not used in revenue service. Both platforms have beige windscreens and red canopies with windows and green frames and outlines in the center that were installed in a 2003 renovation. On either side, there are green, waist-high, ironwork fences. The 125th Street station is the only station on the Manhattan Valley Viaduct, which bridges Manhattanville from 122nd to 135th Streets and has been on the National Register of Historic Places since 1983. The viaduct allows the trains to remain relatively level and avoid steep grades while traversing the valley. The steel arch across 125th Street is long and high. Most of the remainder of the viaduct is a simple steel structure, similar to other early IRT lines, except the approach ramps from 122nd to LaSalle Streets and from 133rd to 135th Streets, which are made of masonry.
Exits
This station has one elevated station house at the center of the platforms and tracks. Two staircases from each side go down to a waiting area/crossunder, where a turnstile bank provides access to and from the station. Outside fare control, there is a token booth and an enclosed passageway on the west side leading to two escalators going down to the west side of Broadway, diverging in opposite directions. One escalator leads to 125th Street while the other leads to Tiemann Place. On the east side of the station house, another enclosed passageway leads to an escalator facing south and going down to the southeast corner of Broadway and 125th Street. Adjacent to this passageway is an "L" shaped staircase with its upper half directly above Broadway and the lower half beneath the enclosed escalator going to the same corner of the intersection.
