The Canarsie Line was first a steam railroad, then a Brooklyn Rapid Transit Company (BRT), later Brooklyn–Manhattan Transit Corporation (BMT), elevated line. It was extended into Manhattan via subway in 1924–1928. Since the early 2000s, the line's signal system has been converted to an automated system. The Manhattan section of the line was partially closed during off-peak hours from early 2019 to April 2020 to allow for a renovation of the 14th Street Tunnel, which the line uses to cross the East River.