[6] The line proceeds as a four-track subway down Seventh Avenue to its intersection with Broadway at Times Square-42nd Street, and then continues down Broadway to a point north of Canal Street, where the express tracks carrying the N and Q services descend and turn sharply east to separate platforms from the local tracks, before crossing the south side of the Manhattan Bridge to go to Brooklyn.

[7] It has been proposed to use this as part of the Lower Manhattan–Jamaica/JFK Transportation Project, connecting to the Court Street station (New York Transit Museum) in Brooklyn.

The original plan there was to build two one-track tunnels under 59th and 60th Streets east of Fifth Avenue, rising onto the bridge to Queens.

[14] On July 28, 1915, the New York Public Service Commission approved a change of plans requested by the New York City Board of Estimate to place both tracks under 60th Street and cross the East River in the 60th Street Tunnel,[15] because of concern whether or not the bridge could handle the weight of all-steel subway trains.

[7][18] South of the Whitehall Street station, provisions were built to allow for two tunnels to Atlantic Avenue in Brooklyn.

[41] Opponents of the plan said it would cause large amounts of confusion, as Times Square was a "natural" transfer point.

[52] During construction, workers discovered the remnants of a tunnel for the Beach Pneumatic Transit near City Hall,[46] as well as the remains of a 17th-century colonial prison near Dey Street.

[57][58] The Public Service Commission approved Dock Contractor's bid despite these objections,[59] and the contract was awarded later that month.

[61] These sections were more than 80 percent complete by March 1914; work on the City Hall station was so far advanced that contractors had begun installing subway entrances.

[62] By February 1914, the Public Service Commission was soliciting bids for a tunnel extending east under Canal Street to the Manhattan Bridge.

Due to the swampy character of the area (which used to contain a drainage canal from Collect Pond), the commission considered building the line using either the cut-and-cover method or using deep-bore tunneling.

The BRT wanted to connect the lines, citing the fact that it would be difficult for passengers to transfer at the Canal Street station or to reroute trains in case of emergency.

[67] Work on the Canal Street line proceeded slowly,[68] in part because of the high water table of the area, which required the contractor to pump out millions of gallons of groundwater every day.

[94] The opening of the line was expected to reduce congestion at Chambers Street, where many BRT passengers had previously transferred to the IRT and paid an extra fare to go uptown.

[95] A short portion of the line, coming off the north side of the Manhattan Bridge through Canal Street to 14th Street–Union Square, opened on September 4, 1917, at 2 P.M., with an eight car train carrying members of the Public Service Commission, representatives of the city government and officials of the BRT, leaving Union Square toward Coney Island.

Service opened to the general public at 8 P.M., with trains leaving Union Square and Coney Island simultaneously.

The opening of this portion of the line provided additional transit service to Times Square, with a new connection to Brooklyn.

[114][112] In the 1960s, the New York City Transit Authority (NYCTA) started a project to lengthen station platforms on the Broadway Line to 615 feet (187 m) to accommodate 10-car trains.

[117] An NYCTA spokesman stated that the old tiles were in poor condition and that the change was made to improve the appearance of stations and provide uniformity.

To replace it in Queens, a new EE local was created, running between Forest Hills and Whitehall Street during weekdays.

Their service from the Bronx and Upper Manhattan continued to run via the Sixth Avenue Line, terminating at 34th Street.

Afterwards, N service began running local via the Broadway Line during evenings, nights, and weekends, but they still operated over the Manhattan Bridge.

Evening and weekend B service stopped switching to the local track north of 34th Street to serve the Astoria Line.

[125][126] On September 30, 1990, express service on the Broadway Line was restored when repair work on the Manhattan Bridge was temporarily suspended.

During late nights, R trains no longer ran via the Broadway Line; instead, they operated as a shuttle in Brooklyn, terminating at 36th Street.

On April 6, 1998, because the service did not terminate at an ADA-accessible station, the shuttle was extended to 34th Street–Herald Square on weekdays, skipping 49th Street via the express tracks.

On February 22, 2004, when the north tracks reopened, the N became express via the Manhattan Bridge and the W was short-turned at Whitehall Street, its Brooklyn section being replaced by the D.[136] On June 25, 2010, because of a budget shortfall, service on the Broadway Line was reduced.

[137] In December 2014, the Q began running local on the line between Canal Street and 57th Street–Seventh Avenue during late nights, to supplement late-night N service.

[138] In early 2016, as part of the upcoming opening of the Second Avenue Subway's first phase, the MTA announced that the W service would resume operations.

[139][140] On November 5, 2016, late-night R service was extended to Whitehall Street in order to reduce the need to transfer and provide a direct link to Manhattan.