The Bx12 is a public transit line in New York City bus route running east-west along 207th Street in Upper Manhattan and along the continuous Fordham Road and Pelham Parkway in the Bronx.

From here, the Bx12 services that do not terminate here make a U-turn and join the New England Thruway to Bay Plaza or veer east along Shore Road to Orchard Beach.

[3][5][10] At the Pelham Bay Park station, Manhattan-bound buses use stops along southbound Amendola Place.

The setup requires westbound service to make a U-turn onto Shore Road before heading onto Pelham Parkway.

[11][12] During the daytime and evening hours, local service runs between Sedgwick/Webb Avenue in University Heights and the Pelham Bay Park subway station (6 and <6>​ trains).

[3][5][10] During the overnight hours, all service runs local, serving the entire route with the exception of Bay Plaza.

Buses instead terminate on Edson Avenue, in front of the Gun Hill Bus Depot, as the shopping center is closed during these times.

[22] That year, the company released plans to extend the line west across the yet-to-be-constructed University Heights Bridge to Broadway and 207th Street in Inwood, Manhattan.

[22][23] By fall 1908, after the opening of the bridge, the Union Railway petitioned for an extension west to Manhattan, and east to Pelham Bay Park.

[25] In 1910, the company once again petitioned the New York City Board of Estimate and the New York State Public Service Commission for a western extension to Manhattan, and for an eastern extension from Southern Boulevard to the eastern edge of Bronx Park (at about Boston Road, White Plains Road, and Bronx Park East).

[28] In late 1916, the railway petitioned for another extension along either Vermilyea Avenue or Nagle Avenue, and Dyckman Street west to the ferry terminal at the end of Dyckman Street, to connect with ferries to New Jersey and upstate New York, particularly the Palisades region and Palisades Interstate Park.

[30] Later, the Union Railway sought to annul the franchise agreement, which was opposed by the local Dyckman (Inwood/Washington Heights) community due to growing business interests created by the line.

[35][36][37] That year, the railroad company began relinquishing its trolley franchises with the city, to be replaced by buses operated by the subsidiary Surface Transportation Corporation.

[41] On April 21, 1989, the New York City Transit Authority presented two proposals to rationalize the eastern terminals of service on the Bx12 to the MTA Board for approval.

The second proposal up for approval was the extension of Bx12 trips that terminated at the Pelham Bay Park subway station to the new Gun Hill Depot at Bartow Avenue and the New England Thruway when it opened in September 1989.

In January 1995, an additional limited stop was added at Jacobi Hospital, and the hours of limited-stop service were expanded from 6:57 – 8:39 a.m. and 4:55 – 6:41 p.m. to 6:30 – 9:30 a.m. and 4 – 6:30 p.m..