Train at Metro Station (photo)

The Chicago L (sometimes written as L or el, 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. It is operated by the Chicago Transit Authority (CTA). It is both the fourth largest rapid transit system in the United States in terms of total route length (at 102.8 miles, and the third busiest rail mass transit system in the United States after the New York City Subway and the Washington Metro. Chicagos L provides 24-hour service on some portions of its network, being one of only four heavy rail rapid transit systems in the United Statesto do so. The oldest sections of the L started operations in 1892, making it the second-oldest rapid transit system in the Americas, after Bostons.