Throughout the 110 year history of the subway, subway cars have evolved continuously and gradually while still working within the structure of what was originally three different subway systems, the Interborough Rapid Transit (IRT), Brooklyn-Manhattan Transit (BMT) and Independent line (IND). Each system operated independently until about 1940 when New York City took control of all three systems. Over the next two decades, they underwent a series of consolidations until 1968 when the Metropolitan Transportation Authority (MTA) was officially established. Remnants of the original identity of each system can be seen in the design of their individual fleet of vehicles even today.
The evolution of subway cars has been both technical and aesthetic, growing from a modified version of a late Victorian wooden railroad coach, to an early twenty-first –century computerized, stainless-steel-and fiberglass subway car.