The 'L' (variously, and sometimes, styled "L", El, EL, or L) is a rapid transit system that serves Chicago in the United States. It is operated by the Chicago Transit Authority (CTA), and is the third busiest rail mass transit system in the United States, behind New York City's New York City Subway, and Washington, D.C.'s Metrorail. The oldest section of the 'L' dates from 1892 making it the second oldest rapid transit system in the Americas after New York (where the oldest operating elevated sections date to the 1880s). It has been credited with helping create the densely built-up downtown that is one of Chicago's distinguishing features.