In the end, the theater was shuttered as it lived: mercifully dark, faintly smelling of body fluids and crammed to capacity with a mixture of starry-eyed young actors and ardent comedy pilgrims, each hoping for an intersection with comic history on an otherwise unremarkable corner of 26th Street.

The line between performer and audience member at the Upright Citizens Brigade Theater in Chelsea — New York’s high temple of improv comedy — was finally obliterated around 1:30 in the morning Wednesday, as seats were vacated and the crowd streamed onto the stage like N.B.A. fans after a championship.

It was the last hurrah at the group’s longest- standing and most storied location, the basement beneath a Gristedes supermarket, which has been its flagship since 2003 (after an earlier stretch in a former strip club). The basement space, soon to be replaced by a new location on 42nd Street, was closely identified with the rotating cast of rising stars who performed there; it was a dank but beloved cradle to household names like Amy Poehler, Aziz Ansari and Kate McKinnon in the unpolished early phases of their careers.

Shannon O’Neill, artistic director of U.C.B.’s New York operation, said in an interview Tuesday that the building’s rough edges became embedded in the group’s DNA.