The connection opened on December 1, 1955, and permitted BMT trains from Brooklyn to use the IND Queens Boulevard Line; the first service to do so was the Brighton Beach Local via Tunnel (1, now Q). Unlike the later Chrystie Street Connection, this was of the nature of a trackage rights operation, without the mixing of BMT and IND equipment or crews, as opposed to a true operating integration.
The first service to use the connection was the daytime 1 local via Montague Street Tunnel, which became the QT in the early 1960s. The QT was rerouted to Astoria – Ditmars Boulevard on January 1, 1961, and the RR was sent through the connection during daytime hours. The EE was created on November 26, 1967, when the Chrystie Street Connection opened and the RR moved back to Astoria. On August 27, 1976, the N was extended through the connection, absorbing the EE; this change sent late night and weekend trains through the tunnel for the first time. The N and R were swapped in Queens on May 24, 1987, taking the R through the connection in a move that reassigned a former BMT route (the R) to the IND's Jamaica Yard (it had heretofore used the Coney Island Yard). Late night service was later truncated to 36th Street in Brooklyn.
Note that this is a list of New York City Subway lines, which are the physical infrastructure over which services operate.
Lines with colors next to them are trunk lines; trunk lines determine the color of New York City Subway service bullets, except for shuttles, which are dark gray.