The first section of what became the current 2 entered service on November 26, 1904, from the temporary 180th Street–Bronx Park terminal via the West Farms El to 149th Street–3rd Avenue.

[7][8][9] On January 9, 1908, the Joralemon Street Tunnel opened, connecting the current IRT Lexington Avenue Line to Brooklyn.

[20] As of 1934, 2 trains ran from 180th Street-Bronx Park to Flatbush Avenue weekdays and Saturday during daytime and to South Ferry evenings and Sundays, running express in Manhattan.

Morning rush hour service to 241st Street was cut back to Gun Hill Road on October 2, 1953.

Beginning on December 12, 1958, late night service was extended to Flatbush Avenue and the 2 began running express at all times.

On weekdays, 2 trains ran via the IRT Lexington Avenue Line between 149th Street–Grand Concourse and Nevins Street uptown from 5:00 a.m. to midnight and downtown from midnight to 5:00 a.m.[26] On October 3, 1999, the 2 began running local in Manhattan during late night hours so local stations would receive service every ten minutes.

[27] On December 9, 1999, New York City Transit released a proposal revising 2 and 5 service in the Bronx to eliminate a merge north of the East 180th Street station, increasing capacity and reducing delays, to the Metropolitan Transportation Authority (MTA) Board.

[28] Shortly after the proposal was more widely announced in April 2000, Assemblyman Jeffrey Klein collected 2,000 signatures for a petition opposing the change.

[30] Opponents of the change also argued that it would have increased subway crowding on the 2 train, especially at the 72nd Street station on the IRT Broadway–Seventh Avenue Line.

The change was also opposed by State Senator Eric Schneiderman, Assemblyman Scott Stringer, and Public Advocate Mark Green.

New York City Transit expected the passenger volume of downtown 2 trains in the morning rush hour to increase from 92% of capacity to 108% at 72nd Street.

[31] After Assembly Speaker Sheldon Silver put pressure on the MTA, the change was pushed back for an additional three months in May 2000.

[32] On September 24, 2000, a spokesperson for New York City Transit said that MTA Chairman E. Virgil Conway told planners to drop the change until service on the 5 was increased with the arrival of new R142 subway cars by early 2002; the swap proposal was canceled the next day.