The tracks at 57th Street were originally built for a proposed extension under Central Park to Harlem. The stub-end tracks were eventually connected to the IND 63rd Street Line when the latter opened in October 1989. The 63rd Street line only extended to the 21st Street–Queensbridge station in Queens, and did not connect to any other lines in that borough. The Q train served the 63rd Street extension on weekdays and the train stopped there on the weekends; both services used the Sixth Avenue Line. The Q train, a part-time express within Brooklyn via the BMT Brighton Line, ran along the Sixth Avenue Line between 1988 and 2001, when the Manhattan Bridge south tracks were closed for reconstruction.