110th Street station (IRT Lexington Avenue Line)

Following the completion of the original subway, there were plans to construct a line along Manhattan's east side north of 42nd Street. The original plan for what became the extension north of 42nd Street was to continue it south through Irving Place and into what is now the BMT Broadway Line at Ninth Street and Broadway. In July 1911, the IRT had withdrawn from the talks, and the Brooklyn Rapid Transit Company (BRT) was to operate on Lexington Avenue. The IRT submitted an offer for what became its portion of the Dual Contracts on February 27, 1912.[6][7]

In 1913, as part of the Dual Contracts, which were signed on March 19, 1913,[8] the Public Service Commission planned to split the original Interborough Rapid Transit Company (IRT) system from looking like a "Z" system (as seen on a map) to an "H"-shaped system. The original system would be split into three segments: two north–south lines, carrying through trains over the Lexington Avenue and Broadway–Seventh Avenue Lines, and a west–east shuttle under 42nd Street. This would form a roughly "H"-shaped system.[9][10] It was predicted that the subway extension would lead to the growth of the Upper East Side and the Bronx.[11][12]

The 110th Street station opened on July 17, 1918, with service initially running between Grand Central–42nd Street and 167th Street via the line's local tracks.[4][13] On August 1, the "H system" was put into place, with through service beginning on the new east and west side trunk lines, and the institution of the 42nd Street Shuttle along the old connection between the sides.[14][15] The cost of the extension from Grand Central was $58 million.[16]

The city government took over the IRT's operations on June 12, 1940.[17][18]

On March 20, 1991, a woman was raped behind a pile of debris in the subway passageway connecting the 34th Street–Herald Square and 42nd Street–Bryant Park stations under Sixth Avenue during rush hour, which had entrances at 38th Street. This was the longest passageway in the system. That passageway was closed the day after[19] and recorded 30 felonies since January 1, 1990. In response, on March 28, 1991, the NYCTA ordered the closing of the 15 most dangerous passageways in the system within a week, which the Transit Police and citizen advocacy groups had called for since the previous year.[20] The locations were chosen based on crime volume, lighting, traffic and physical layout. These entrances were closed under the declaration of a public safety emergency, and were blocked off with plywood and fencing until public hearings were held and official permission was obtained.[21] One of the stations that had an entrance closed was 110th Street, which has the exit-only staircase at 111th Street from the northbound platform closed. 52 felonies had occurred at the station since January 1, 1990.[22] The entrance was permanently closed in 1992, following a public hearing.[23]

In June 2002, it was announced that 110th Street would be one of ten subway stations citywide to receive renovations. Work on these ten renovation projects was estimated to cost almost $146 million, and was scheduled to start later that year, and be completed in April 2004. The renovation projects made repairs to platforms, replaced or refurbished stairways, installed new lighting and tiles, and reconfigured fare control areas.[24]

In May 2018, New York City Transit Authority President Andy Byford announced his plan subway and bus modernization plan, known as Fast Forward, which included making an additional 50 stations compliant with the Americans with Disabilities Act of 1990 during the 2020–2024 Metropolitan Transportation Authority (MTA) Capital Program to allow most riders to have an accessible station every two or three stops.[25][26] The draft 2020–2024 Capital Program released in September 2019 included 66 stations that would receive ADA improvements.[27] In December, the MTA announced that an additional twenty stations, including 110th Street, would be made ADA-accessible as part of the Capital Program.[28][29]

Each platform has one same-level fare control area at the center. Each one has a turnstile bank, token booth, and two street stairs. The ones on the southbound platform go up to either western corners of Lexington Avenue and 110th Street, while the ones on the northbound platform go up to either eastern corners. There are no crossovers or crossunders to allow a free transfer between directions.[35] Both platforms used to have second exits at their northern ends to 111th Street.[36][37][38] The entrance on the northbound platform to the southeastern corner of 111th Street and Lexington Avenue was closed due to safety reasons in 1992[23] and was subsequently slabbed over. The only evidence of this exit is a steel door in the wall.[39] The entrance on the northbound platform closed some time before 1992.