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. In 2023, the system had a ridership of 279,146,200, or about 908,400 per weekday as of the fourth quarter of 2023.

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 States in terms of total route length, at 102.8 miles (165.4 km) long as of 2014, and the third-busiest rapid transit system in the United States. In 2016, the "L" had 1,492 rail cars, eight different routes, and 145 train stations. In 2023, the system had 117,447,000 rides, or about 373,800 per weekday in the fourth quarter of 2023.