[4]: 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.

[5]: 3  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,[6] in which it would construct the subway and maintain a 50-year operating lease from the opening of the line.

[7]: 83–84 [8]: 260–261  Contract 2, which gave the IRT a 35-year lease,was executed between the commission and the Rapid Transit Construction Company on September 11, 1902.

[10] Belmont submitted a revised proposal to the Rapid Transit Commission in April 1905 to widen the line to four tracks.

[11][12] Work was halted until October 1905, at which point two tracks had been added, making four under Fulton Street and five under Flatbush Avenue.

The lower level had one trackway and platform in the station, with two connections on each side, all built at great cost under existing work, but none of it was ever used.

[23][26] As part of the Dual Contracts, approved in 1913, the New York City Public Service Commission planned to split the original IRT system into three segments: two north-south lines, carrying through trains over the Lexington Avenue and Broadway–Seventh Avenue Lines, and an east–west shuttle under 42nd Street.

[27] The Broadway–Seventh Avenue Line would split into two branches south of Chambers Street, one of which would turn eastward through Lower Manhattan, run under the East River via a new Clark Street Tunnel, and connect with the existing Contract 2 IRT Brooklyn Line at Borough Hall.

[30] This was followed by the Clark Street Tunnel on April 15, 1919,[31][32] which doubled the number of IRT trains that could travel between Manhattan and Brooklyn.

[38] The New York City Board of Transportation announced plans in November 1949 to extend platforms at several IRT stations, including Nevins Street, to accommodate all doors on ten-car trains.

Although ten-car trains already operated on the line, the rear car could not open its doors at the station because the platforms were so short.

[41] The New York City Transit Authority (NYCTA) announced plans in 1956 to add fluorescent lights above the edges of the station's platforms.

The mezzanine walls feature a mosaic frieze by Anton von Dalen, installed in 1997 and entitled Work & Nature.

It features stenciled silhouettes in black of a woman operating a sewing machine, a mother taking care of a child, a man planting a tree, an architect reading a blueprint, a female executive addressing a meeting, and famous musician Furry Lewis.

At its north end, this trackway splits from the southbound local track just south of Hoyt Street, and starts heading downgrade.

On the other side, it rises again to merge with the southbound local track in the midst of the complicated switch layout just north of Atlantic Avenue – Barclays Center.

Before Nevins Street, there is a bellmouth for the proposed Lafayette Avenue subway that merges into the northbound local track.

For a time in the early 1960s, a false wall was installed to seal the ramp to the Nevins Street lower level.