[3]: 21 However, development of what would become the city's first subway line did not start until 1894, when the New York State Legislature passed the Rapid Transit Act.
It called for a subway line from New York City Hall in lower Manhattan to the Upper West Side, where two branches would lead north into the Bronx.
[3]: 148 The Rapid Transit Construction Company, organized by John B. McDonald and funded by August Belmont Jr., signed the initial Contract 1 with the Rapid Transit Commission in February 1900,[5] in which it would construct the subway and maintain a 50-year operating lease from the opening of the line.
[4]: 4 Belmont incorporated the Interborough Rapid Transit Company (IRT) in April 1902 to operate the subway.
An order issued by the United States War Department required that the top of the subway tunnel be at least 20 feet (6.1 m) below the tide level of the river.
As a result, the tubes sloped downward at a 3 percent grade on either side of the river; these were the steepest sections of track built in Contract 1.
[6]: 252 Since the river bed contained clay, silt, and irregular rock, it could not be excavated using a conventional shield.
Instead, the contractor suggested building a submerged rectangular cofferdam extending from the shore to the middle of the river, then excavating the riverbed and constructing the tunnel one half at a time.
[11] In 1906, West Farms express trains began operating through to Atlantic Avenue in Brooklyn.
[12] To address overcrowding, in 1909, the New York Public Service Commission proposed lengthening the platforms at stations along the original IRT subway.
[13]: 168 As part of a modification to the IRT's construction contracts made on January 18, 1910, the company was to lengthen station platforms to accommodate ten-car express and six-car local trains.
[14]: 113 On January 23, 1911, ten-car express trains began running on the West Farms Branch.
As part of Contract 3, the IRT agreed to build an elevated line along Jerome Avenue in the Bronx.
[30] The New York City Transit Authority (NYCTA) announced plans in 1956 to add fluorescent lights above the edges of the Jerome Avenue Line station's platforms.
[32] As part of the MTA's 2015–2019 Capital Program, all platforms at the 149th Street–Grand Concourse station are planned to receive full ADA accessibility.
The 149th Street–Grand Concourse station on the IRT White Plains Road Line has two tracks and two side platforms.
[50] Today, all of the original mosaic "Mott Avenue" name tablets have been covered over with metal "149 St–Grand Concourse" signs.
Only one name tablet, located on the downtown platform between the last two staircases at the northern end, remained uncovered and survived intact until a few years into the 21st century when a serious water leak after very heavy rainfall caused individual tiles to separate from the wall and fall off.
Due to high usage levels and the sharp turn of the connection, it often causes delays on the 5 train.
The western ends of the platforms were truncated in 1918 to allow the construction of the track connection to the Jerome Avenue Line.