Chicago &quot;L&quot;

The Chicago "L" (short for "elevated railway") is the Chicago rapid transit system. It serves the city of Chicago and some of its surrounding suburbs in the U.S. state of Illinois. 
The "L" is operated by the Chicago Transit Authority (CTA). It is the fourth-largest rapid transit system in the United States. It is long, and the second-busiest rail mass transit system in the United States, after the New York City Subway.
Chicago's "L" has 24-hour service on some portions of its network. It is one of only five rapid transit systems in the United States to do so. The oldest sections of the Chicago "L" started operations in 1892, making it the second-oldest rapid transit system in the Americas, after New York City's elevated lines.