Its route emblem, or "bullet", is colored medium gray since it serves the BMT Canarsie Line.

[4] The L operates 24 hours a day between Eighth Avenue in Chelsea, Manhattan, and Rockaway Parkway in Canarsie, Brooklyn, making all stops along the full route.

[9] Starting on September 23, 1936, express trains ran to Lefferts Boulevard via the connection with the Fulton Street Elevated at Atlantic Avenue.

[10] This connection was severed on April 30, 1956, then the service ran to Rockaway Parkway again, but was discontinued on August 23.

On November 26, 1967, with the opening of the Chrystie Street Connection, the BMT Eastern Division lines were given letters.

The 14 to Canarsie was given the label JJ (though the 14 main line was designated KK, continuing east from Broadway Junction towards Jamaica).

The Metropolitan Transportation Authority's $443 million fleets of subway cars on the L was introduced in 2002, but by 2006 was already too small to handle growing ridership.

Therefore, sixty-four new R160A cars manufactured by Alstom were equipped with CBTC so they could run on the L. The BMT Canarsie Line tracks underwent an extensive retrofit over to CBTC, a system that controls the trains via a computer onboard, as opposed manually operated by a human operator.

The line also used OPTO (one person train operation) beginning in June 2005, but a combination of public outcry regarding perceived safety issues, which increased after the July 2005 London tube bombings, heavy lobbying by the Transport Workers Union of America (TWU), as well as an arbitration ruling that MTA had breached its contract with TWU caused the Metropolitan Transportation Authority to end OPTO the following September.

[21] On April 26, 2020, New York governor Andrew Cuomo announced the completion of the project, months ahead of schedule.