The IND Eighth Avenue Line is a rapid transit line in the B Division of the New York City Subway. Opened in 1932, it was the first line of the Independent Subway System (IND); as such, New Yorkers originally applied the Eighth Avenue Subway name to the entire IND system.: "the property is near the Woodhaven Boulevard station of the Eighth Avenue subway": "the Jamaica inspection barn of the Eighth Avenue Subway System, in Kew Gardens, Queens"

The line runs from 207th Street in Inwood south to an interlocking south of High Street in Brooklyn Heights, including large sections under St. Nicholas Avenue, Central Park West, and Eighth Avenue. The entire length is underground, though the 207th Street Yard, which branches off near the north end, is on the surface. Flying junctions are provided with the IND Concourse Line, IND Sixth Avenue Line, and IND Queens Boulevard Line.

Most of the line has four tracks, with one local and one express track in each direction, except for the extreme north and south ends, where only the two express tracks continue. Internally, the line is chained as Line "A", with tracks A1, A3, A4, and A2 from west to east, running from approximately 800 at the south end to 1540 at the north end (measured in hectofeet).

The whole line is served at all times by the A train, which runs express except during late nights. The C provides local service south of 168th Street while the A runs express. In addition, the B provides weekday local service and the D full-time express service between the Concourse Line (145th Street) and Sixth Avenue Line (59th Street–Columbus Circle) junctions, and the E runs local from the Queens Boulevard Line junction at 50th Street south to World Trade Center. The A, C, and E are colored on signs because they run via Eighth Avenue through Midtown Manhattan, while the B and D are since they use the Sixth Avenue Line through Midtown Manhattan.

Extent and service The following services use part or all of the Eighth Avenue Line. The trunk line's bullets are colored :  Time periodSection of linerush hours, middays,and eveningsweekendslate nightsexpresslocalentire linelocalno servicesouth of 168 Stlocalbetween 50 St and WTClocalno servicebetween 145 St and 59 Stexpressbetween 145 St and 59 St

The Eighth Avenue Line begins as a two-track subway under Broadway at 207th Street in Inwood. A flying junction just to the south brings two tracks from the 207th Street Yard between the main tracks, merging after Dyckman Street. The subway leaves Broadway to pass under Fort Tryon Park to the north end of Fort Washington Avenue, which it follows to roughly 175th Street before turning southeast under private property.

The small 174th Street Yard lies under Broadway, with two tracks exiting to the south under that roadway. When the George Washington Bridge was designed in the 1920s, provisions were made for a lower deck that would carry these two tracks north from the yard and across the bridge, as well as two commuter rail tracks. However, when the lower level was added in 1962, it instead carried a roadway.

The two main tracks from Fort Washington Avenue enter Broadway near 172nd Street, curving and running underneath a public school (PS173M) at 174th Street, and other private property, and the yard tracks in a double-decker tunnel. A few blocks later, the lower tracks separate to straddle the yard tracks at 168th Street. The local/express split begins here, with the local tracks coming from the yard and the express tracks coming from Inwood. Contrary to standard practice, the two local tracks are in the center and the two express tracks are on the outside. Except during late nights, the local service (C) ends at 168th Street, reversing direction on the yard tracks; the A runs to 207th Street at all times, express except during late nights. South of 168th Street, the express (outer) tracks lower below the local tracks, forming another double-decker tunnel, this time under St. Nicholas Avenue.

North of 145th Street, the lower (express) tracks rise into the center, and the three-track IND Concourse Line enters St. Nicholas Avenue below the four-track Eighth Avenue Line. 145th Street is a two-level transfer station, with two island platforms on each level. To the south, the Concourse Line tracks rise and merge with the Eighth Avenue Line, carrying the B onto the local tracks and the D onto the express tracks. The resulting four-track line continues south under St. Nicholas Avenue and Eighth Avenue (Frederick Douglass Boulevard), which becomes Central Park West at 110th Street.

Most of the line under Central Park West is built on two levels with both local tracks to the west and only local stations. The two northbound tracks are above the two southbound tracks. Approaching 59th Street–Columbus Circle, where Central Park West becomes Eighth Avenue, the subway again spreads out into a single four-track level.

A flying junction south of 59th Street takes B and D trains east under 53rd Street, merging with two tracks from 57th Street to become the four-track IND Sixth Avenue Line. The two-track IND Queens Boulevard Line, also in 53rd Street, curves south into a lower level of the 50th Street station, and merges to the south, taking E trains onto the local tracks. An unused southbound-only lower level at 42nd Street–Port Authority Bus Terminal was formerly accessed only from the southbound track from the Queens Boulevard Line. Plans for the 7 Subway Extension required partially demolishing the lower level to make room for the new IRT Flushing Line tracks.

The four-track line continues south under Eighth Avenue to 14th Street, where it turns southeast under Greenwich Avenue and south under Sixth Avenue, above the four-track IND Sixth Avenue Line. The two-level West Fourth Street–Washington Square station allows easy transfers between the two lines. Just to the south are track connections between the local tracks of each line, not used by current normal service patterns. The Sixth Avenue Line turns east into Houston Street after passing the connections.

Canal Street, under Sixth Avenue, is the last normal four-track station on the line. Crossovers in each direction, beyond the station, take C and late night A trains between the local tracks to the north and the express tracks to the south. As the subway turns from Sixth Avenue into Church Street, the southbound local track passes under the express tracks, bringing E trains to the east. At this point, a bellmouth originally intended for the never-built IND Worth Street Line is present on the east side of the tunnel. It has been proposed to use this to bring Long Island Rail Road Atlantic Branch trains to Lower Manhattan as part of the Lower Manhattan-Jamaica/JFK Transportation Project.

The four tracks continue south under Church Street, with two separate but connected stations at World Trade Center at the end of the local tracks and Chambers Street on the express tracks. The two express tracks turn east under Fulton Street, crossing the East River through the Cranberry Street Tunnel into Cranberry Street in Brooklyn. Cranberry Street leads to High Street, from which the line turns south into Jay Street, straddled by the two-track IND Sixth Avenue Line from the Rutgers Street Tunnel. The Eighth and Sixth Avenue Lines end, becoming the IND Fulton Street Line and IND Culver Line, at crossovers (currently unused) allowing trains to switch between the two, located between High Street and Jay Street–MetroTech. Both the A and C trains continue along the Fulton Street Line.

History

Planning and construction

As early as March 1918, soon after the BMT Broadway Line opened to Times Square–42nd Street, plans were being considered for an extension of that line beyond the stubs at 57th Street–Seventh Avenue to the Upper West Side and Washington Heights via Central Park West (Eighth Avenue). On August 3, 1923, the New York City Board of Estimate approved the Washington Heights Line, an extension of the Broadway Line to Washington Heights. The line was to have four tracks from Central Park West at 64th Street under Central Park West, Eighth Avenue, Saint Nicholas Avenue, and private property to 173rd Street, and two tracks under Fort Washington Avenue to 193rd Street. South of 64th Street, one two-track line would connect to the Broadway Line stubs at 57th Street, and another would continue under Eighth Avenue to 30th Street at Penn Station, with provisions to continue downtown.

Mayor John Hylan instead wanted to build an independent subway system, operated by the city. The New York City Board of Transportation (NYCBOT) gave preliminary approval to several lines in Manhattan, including one on Eighth Avenue, on December 9, 1924. The main portion of the already-approved Washington Heights Line—the mostly-four track line north of 64th Street—was included, but was to continue north from 193rd Street to 207th Street. South of 64th Street, the plan called for four tracks in Eighth Avenue, Greenwich Avenue, the planned extension of Sixth Avenue, and Church Street. Two tracks would turn east under Fulton Street or Wall Street and under the East River to Downtown Brooklyn.

A groundbreaking ceremony was held at St. Nicholas Avenue and 123rd Street on March 14, 1925. Most of the Eighth Avenue Line was dug using a cheap cut-and-cover method, where the street above was excavated. Still, the construction of the line was difficult, as it had to go under or over several subway lines. At 59th Street–Columbus Circle, workers had to be careful to not disrupt the existing IRT Broadway–Seventh Avenue Line overhead. 42nd Street, the longest station along the line at , was expected to be a major express station with large platforms, so the platforms were staggered away from each other in order to avoid going under property lines. Additionally, several workers died in cave-ins during construction.

In the summer of 1926 the BOT held a public hearing and agreed upon the details of the construction of the subway line under Church Street. As part of the construction of the line, Church Street was widened from being wide to being wide to accommodate the subway underneath and was connected with a southern diagonal extension of Sixth Avenue, which was . Had the street not been widened the construction would have cost an additional $7 million for the construction of a two-level subway structure. In January 1929, the city paid money awarded to adjacent property owners for property taken and awarded contracts for -wide sidewalks and a -wide roadway. The sidewalks had been wide and the roadway had been wide. New buildings were built on the west sides of Church Street. The east side of the street was not affected by the construction. $9,631,760 was awarded to 161 property owners whose property had been taken. 168,888 square feet of land had to be acquired to widen Church Street between Park Place and Canal Street.

In 1926 construction began on the extension of Sixth Avenue south from Carmine Street to Canal Street, to allow for the construction of the Eighth Avenue Line (which runs under the street south of Eighth Street), and to provide access to the Holland Tunnel. The construction of the extension was completed in 1930. The city condemned entire lots, displacing 10,000 people, to build the extension and used leftover land for parks.