The Chicago Rapid Transit Company (CRT) was a privately owned firm providing rapid transit rail service in Chicago, Illinois and several adjacent communities between the years 1924 and 1947. The CRT is one of the predecessors of the Chicago Transit Authority, Chicago's current mass transit operator. The CRT was an amalgamation of several elevated railroad operators, each of which operated service in a particular section of the city. These predecessors include: The CRT network was entirely at or above grade level until the 1943 opening of the State Street subway, now part of CTA's Red Line.