[3][4] The IRT also sought to operate a north–south route in Manhattan along Seventh Avenue south of Times Square.

[5] The Seventh Avenue and 14th Street lines were both assigned to the BRT in 1911 after the IRT refused to agree to a compromise over the Tri-borough system.

[16] It was predicted that the subway extension would lead to the growth of the Lower West Side, and to neighborhoods such as Chelsea and Greenwich Village.

[17][18] As part of the Dual Contracts, the IRT was authorized to construct an express station on its Seventh Avenue Line at 14th Street.

[21][22] This contract was awarded in March 1914 to the United States Realty and Investment Company, who made a low bid of $1.837 million.

[30][32] The new "H" system was implemented on August 1, 1918, joining the two halves of the Broadway–Seventh Avenue Line and sending all West Side trains south from Times Square.

The BRT was authorized to construct a station on its Canarsie Line at Sixth Avenue and 14th Street.

[19][20] In late 1915, the Public Service Commission began receiving bids for the construction of the 14th Street Line.

[35][36] Booth and Flinn was awarded the first contract for the line, namely a tunnel under the East River, in January 1916.

[49] New York City mayor John Francis Hylan's original plans for the Independent Subway System (IND), proposed in 1922, included building over 100 miles (160 km) of new lines and taking over nearly 100 miles (160 km) of existing lines, which would compete with the IRT and the BMT, the two major subway operators of the time.

[56] However, the IND had not yet finalized the locations of Sixth Avenue Line stations between 42nd and Fourth Streets because it was still negotiating with the H&M.

[58][59] The final contract for the line, covering the section between 9th and 18th Streets, was awarded to Spencer White & Prentis in June 1937.

[63] Builders had to use very small charges of dynamite so that they would not disrupt the H&M tunnels alongside the route, the street and elevated line above, and the water main below.

[77] In 2018, the MTA allocated some funding for Americans with Disabilities Act of 1990 (ADA) improvements at the Sixth Avenue/14th Street station.

[83] Between February 27, 2023, and December 11, 2023, the transfer passageway between Sixth and Seventh Avenues was closed for the installation of elevators and reconfiguring of the ramp as a part to make the station compliant with the ADA.

[96] The track walls on both sides of the platform have their original IRT mosaic trim line with "14" tablets on it at regular intervals.

Both platforms have blue I-beam columns that run along both sides at regular intervals with alternating ones having the standard black station name plate in white lettering.

The mezzanine has a now-unused customer assistance booth and two staircases going up to both northern corners of 12th Street and Seventh Avenue.

Beneath the trim line and name tablets are small directional and number tile captions in white lettering on a black background.

Forest green I-beam columns run along both platforms at regular intervals with alternating ones having the standard black name plate with white lettering.

Trains open their doors to the left in both directions, which is unusual for a side platformed station in New York City.

The deep-bore tunnel's round shape becomes square below this station and at 23rd Street, where provisions for lower-level platforms were built.

[103] West of the station, a center lay-up track begins at a bumper block and is only accessible from the Eighth Avenue terminal.

The two westernmost ones go up to a passageway that leads to the full-time fare control area at the IRT Broadway–Seventh Avenue Line station.

[97] Another unstaffed bank of turnstiles by the northeast staircase leads to the mezzanine above the Queens-bound platform of 14th Street on the IND.

[97] The last staircase on the extreme east end of the platform leads to a storage area and ventilation room.