CTA trains, Chicago, Illinois, United States: The Chicago Transit Authority (CTA) is the operator of mass transit in Chicago, Illinois, United States, and some of its suburbs, including the trains of the Chicago "L" and CTA bus service. The Chicago "L" is the rapid transit system serving the city of Chicago and some of its surrounding suburbs in the U.S. state of Illinois. Operated by the Chicago Transit Authority (CTA), it is the fourth-largest rapid transit system in the United and the third-busiest rapid transit system in the United States after the New York City Subway and the Washington Metro. Wikipedia


















