After the September 11 attacks , all ' '' 1 ' '' trains had to be rerouted since the IRT Broadway – Seventh Avenue Line ran directly under the World Trade Center site and was heavily damaged in the collapse of the Twin Towers . ' '' 1 ' '' trains ran only between 242nd Street and 14th Street , making local stops north of and express stops south of 96th Street . The skip-stop service with the ' '' 9 ' '' train was suspended . On September 19 , after a few switching delays at 96th Street , service was changed . All ' '' 1 ' '' trains made all stops from 242nd Street to New Lots Avenue via the Clark Street Tunnel and IRT Eastern Parkway Line , to replace all '' '' '' trains ( which terminated at 14th Street ) at all times except late nights , when it terminated at Chambers Street in Manhattan instead . On September 15 , 2002 , all ' '' 1 ' '' trains returned to the South Ferry Loop and ' '' 9 ' '' skip-stop service was reinstated . Cortlandt Street , which was directly underneath the World Trade Center , was demolished as part of the clean-up , to be rebuilt as part of the World Trade Center Transportation Hub
September 11 attacks
September 11 attacks
IRT Broadway–Seventh Avenue Line