The New York City Subway is a rapid transit system that serves four of the five boroughs of New York City, New York: the Bronx, Brooklyn, Manhattan, and Queens. Its operator is the New York City Transit Authority, which is itself controlled by the Metropolitan Transportation Authority of New York. In 2015, an average of 5.65 million passengers used the system daily, making it the busiest rapid transit system in the United States and the 11th busiest in the world. The present New York City Subway system is composed of three formerly separate systems that merged in 1940: the Interborough Rapid Transit Company (IRT), the Brooklyn–Manhattan Transit Corporation (BMT), and the Independent Subway System (IND). The privately held IRT, founded in 1902, constructed and operated the first underground railway line in New York City. The opening of the first line on October 27, 1904, is commonly cited as the opening of the modern New York City Subway, although some elevated lines of the IRT and BMT that were initially incorporated into the New York City Subway system but then demolished predate this. The oldest sections of elevated lines still in operation were built in 1885. The BMT, founded in 1923 and also privately held, was formed from the bankruptcy of the Brooklyn Rapid Transit Company. The IND was created by the City of New York in 1921 to be a municipally owned competitor of the two private companies. Unification in June 1940 by the New York City Board of Transportation brought the three systems under one operator. The New York City Transit Authority, created in 1953 to be a public benefit corporation that acquired the rapid transit and surface line (buses and streetcars) infrastructure of the Board of Transportation, remains the operator of the New York City Subway today. The official count of stations is ; however, this tabulation classifies some transfer stations as two or more stations, which are called "station complexes" within the nomenclature of the New York City Subway. If station complexes are counted as one station each, the number of stations is . Thirty-two such station complexes exist. The reason for the higher count generally lies in the history of the New York City Subway: IRT, BMT and IND stations are usually counted separately, particularly if their lines are not parallel and are adjacent to or on another level to each other. Regardless of how stations