The starts in Manhattan and ends in Brooklyn. All but two stations on the Brooklyn leg are served by the in some capacity, whereas all but two stations on the entire route are served by the in some capacity. Brooklyn IRT ridership leans heavily toward Lexington Avenue, whereas Manhattan ridership simply seeks a train. East of Franklin Avenue, there are no real draws, and connections are typically fairly easy to make with other trains. Hell, until about 20 years ago, it ran using 9-car trains, only ending the practice in order to be a more capable supporter. (Its support role is, in fact, the only thing keeping it around. Even taking the night service into account, it's clear that its existence hangs from a thread, as most who actually care about it use one of the two stations with no regular service whatsoever, and the MTA will point to the buses in a heartbeat.)