1
The 1 began running between 1904 and 1908 on the West Side Branch, which it still currently runs on. It ran from 242 Street in the Bronx to Lower Manhattan. The tracks below 96th Street would let the train run locally to South Ferry or express to New Lots Avenue, Brooklyn, until 1959. On June 3, 1917, the first stretch of track between Times Square - 42nd Street and 34th Street - Penn Station opened. Between 1989 and 2005, the 1 had a rush hour variant like the J and the Z called the 9 train. The 9 train line ran on a skip-stop route but was eventually shut down because of inefficiency due to longer wait times at these stations. After 9/11, the 9 was temporarily suspended, and the 1 was rerouted to terminate service at the southern terminal of Chambers Street. Eventually, the 1 would permanently have its southern terminal changed to terminate service at South Ferry.
2
The 2 would begin service on November 26, 1904, running between 180th Street - Bronx Park and 149th Street - 3rd Avenue. In 1908, the Joralemon Street Tunnel opened, connecting Downtown Brooklyn to Lower Manhattan (Brooklyn to Battery). 2 trains began running to Borough Hall via this tunnel and would later be extended to end at Nevins Street, then Atlantic Avenue. In 1920, the northern terminal was moved from 180th Street to Wakefield - 241st Street, where it currently terminates service. In 1918, all three of the IRT Broadway–Seventh Avenue Lines were completed. The next year, the Clark Street tunnel would open, and the 2 and 3 trains would travel into Brooklyn via this tunnel rather than the Joralemon one. In 1928, the New York State Transit Commission wanted to increase the distance covered by the trains and extended the southern terminal to Flatbush Avenue, solidifying the route the 2 runs today.
3
On November 23, 1904, the IRT Lenox Avenue Line opened between 96th Street and 145th Street. 3 trains that ran along this line would make all local stops between 14th Street and City Hall. The 3 would run between 145th Street and South Ferry but would terminate service at 96th Street during late nights. This route would be eliminated in 1955 due to low passenger numbers, leading to the 145th Street Station being closed and the line extended to Flatbush Avenue, where the 2 ended service. It would run to Flatbush Avenue for five years until 1960, when the southern terminal was rerouted to New Lots Avenue. In 1968, the 148th Street - Lenox Terminal was completed, and the 3 train would run along it.
