The Loop (historically Union Loop) is the two mile circuit of elevated railroad that forms the hub of the 'L' rapid transit system in Chicago, Illinois. The Loop is so named because the railroad loops around a rectangle formed by Lake Street (north side), Wabash Avenue (east), Van Buren Street (south), and Wells Street (west). The surrounding area is also known as The Loop community area. Numerous accounts assert that the use of this term predates the elevated railroad, deriving from the multiple cable car turntables, or loops, that terminated in the district, and especially those of two lines that shared a loop, constructed in 1882, bounded by Madison, Wabash, State, and Lake. However, after extensive research of the issue, transportation historian Bruce Moffat concluded that "the Loop" was not used as a proper noun until after Charles Yerkes' 1895–97 construction of the elevated hub.
The Loop includes nine stations: Clark/Lake and State/Lake are on the northern leg; Randolph/Wabash, Madison/Wabash, and Adams/Wabash are on the eastern side; Library and LaSalle/Van Buren are on the southern leg; and Quincy and Washington/Wells are on the western side. In 2009 20,086,763 passengers entered the 'L' via these stations.
Five of the eight 'L' lines use the Loop tracks. Two of the remaining three lines, Blue Line and Red Line, run underground through the center of the loop, connecting to loop stations. The Yellow line is the only CTA line that does not run on or connect to the loop.