The north end of the Crosstown Line is a flying junction with the IND Queens Boulevard Line and 60th Street Tunnel Connection just south of Queens Plaza. The line then travels south as a two-track line, except for a center relay track south of Court Square. At the turn from Marcy Avenue to Lafayette Avenue, two center tracks appear, merging into one after crossovers to the main tracks. These tracks were to be used for a split to another line in a 1931 expansion plan. This center track continues through Bedford–Nostrand Avenues and then ends with crossovers to the main tracks, but space remains in the center at least through Classon Avenue for the third track.
At Hoyt–Schermerhorn Street, the Crosstown Line comes passes through the middle of the four-track IND Fulton Street Line. Cross-platform transfers are available between the lines, but no track connections exist. After Hoyt–Schermerhorn Street, the line turns south and ends as a merge into the local tracks of the IND Culver Line, just south of the split of that line into local and express tracks.
Plans for a crosstown line from the Queensboro Bridge under Jackson Avenue, Manhattan Avenue, Roebling Street, Bedford Avenue, and Hancock Street to Franklin Avenue at the north end of the BMT Franklin Avenue Line were adopted by the city in 1923, but, the following year, Mayor Hylan decided to oppose it. Eventually the line was moved and incorporated into the city's Independent Subway System.
On August 19, 1933, the line was opened north of Nassau Avenue, and the GG began operations to Queens Plaza. The Crosstown Line was completed to the IND Culver Line on July 1, 1937, and the GG was extended in both directions to Smith–Ninth Streets and Forest Hills–71st Avenue. On December 16, 2001, the 63rd Street Connection opened. Since then, G trains (renamed from GG in 1986) have terminated at Court Square during midday and rush hours (replaced by the V service beyond to Forest Hills).
|Station||Opened||Transfers and notes|
|Splits from the IND Queens Boulevard Line ()|
|Long Island City–Court Square||August 19, 1933||IRT Flushing Line at 45th Road–Court House Square ()|
IND Queens Boulevard Line at 23rd Street–Ely Avenue
|21st Street||August 19, 1933|
|Greenpoint Avenue||August 19, 1933|
|Nassau Avenue||August 19, 1933|
|Metropolitan Avenue||July 1, 1937||BMT Canarsie Line at Lorimer Street|
|Broadway||July 1, 1937|
|Flushing Avenue||July 1, 1937|
|Myrtle–Willoughby Avenues||July 1, 1937|
|Bedford–Nostrand Avenues||July 1, 1937|
|Classon Avenue||July 1, 1937|
|Clinton–Washington Avenues||July 1, 1937|
|Fulton Street||July 1, 1937|
|Hoyt–Schermerhorn Streets||July 1, 1937||IND Fulton Street Line|
|Merges with the IND Culver Line ()|