Interborough Rapid Transit Company

The Interborough Rapid Transit Company (IRT) was a rapid transit company in New York City. It operated from 1904 to 1940, when the NYC Board of Transportation merged it with the Independent Subway System (IND) and Brooklyn-Manhattan Transit Corporation (BMT) to create the current NYC Subway system. The NYC Subway's A Division lines (1/2/3/4/5/6/7/S) are former IRT lines, while the B Division was formerly operated by the IND and BMT. It owned NYC's first public subway line.