The Chicago "L" (short for "elevated") 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 rail mass transit system in the United States, after the New York City Subway and the Washington Metro. In 2016, the "L" had 1,492 rail cars, eight different routes, and 145 train stations. In 2021, the system had 78,623,200 rides, or about 294,000 per weekday in the fourth quarter of 2021.
The "L" provides 24-hour service on the Red and Blue Lines and is one of only five rapid transit systems in the United States to do so. The oldest sections of the "L" started operations in 1892, making it the second-oldest rapid transit system in the Americas, after New York City's elevated lines.
The "L" has been credited for fostering the growth of Chicago's dense city core that is one of the city's distinguishing features. It consists of eight rapid transit lines laid out in a spoke–hub distribution paradigm focusing transit towards the Loop. The "L" gained its name because large parts of the system run on elevated track. However, portions of the network are also in subway tunnels, at grade level, or in open cuts.In a 2005 poll, Chicago Tribune readers voted it one of the "seven wonders of Chicago", behind the lakefront and Wrigley Field, but ahead of Willis Tower (formerly the Sears Tower), the Water Tower, the University of Chicago, and the Museum of Science and Industry.