Chicago "L", U.S.A.

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. It is operated by the Chicago Transit Authority. 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 and third busiest rail mass transit system in the USA after Washington Metro. Chicago's "L" provides 24-hour service on some portions of its network, being one of only four heavy rail rapid transit systems in the United States. The oldest sections of the "L" started operations in 1892, making it the second-oldest rapid transit system in the Americas, after Bostons “T”. The "L" has been credited with fostering the growth of Chicago's dense city core that is one of the city's distinguishing features. The "L" consists of eight rapid transit lines laid out in a spoke-hub distribution paradigm mainly focusing transit towards the Loop. Although the "L" gained its nickname because large parts of the system are elevated, portions of the network are also in subway tunnels, at grade level, or open cut.