The New York City Subway is a rapid transit system that serves four of the five boroughs of New York City in the U.S. state of New York: the Bronx, Brooklyn, Manhattan, and Queens. Its predecessors—the Interborough Rapid Transit Company (IRT), the Brooklyn–Manhattan Transit Corporation (BMT), and the Independent Subway System (IND)—were consolidated in 1940. Since then, stations of the New York City Subway have been permanently closed, either entirely or in part.