The Blue Line is a 26.93-mile-long (43.34 km) Chicago "L" line which extends through The Loop from O'Hare International Airport at the far northwest end of the city, through downtown via the Milwaukee–Dearborn subway and across the West Side to its southwest end at Forest Park, with a total of 33 stations (11 on the Forest Park branch, 9 in the Milwaukee–Dearborn subway and 13 on the O'Hare branch). At about 27 miles, it is the longest line on the Chicago "L" system and second busiest, and one of the longest local subway/elevated lines in the world. It has an average of 47,120 passengers boarding each weekday in 2021. Chicago's Blue Line and Red Line offer 24-hour service, everyday, year-round. This makes Chicago, New York City, and Copenhagen the only three cities in the world to offer local nonstop rail service throughout their city limits 24-hours a day, seven days a week. The Blue Line is one of two lines in Chicago with more than one station having the same name, with the Green Line being the other. (The Blue Line has two stations at Harlem Avenue: one in the Kennedy Expressway on the Northwest side and one on the Eisenhower Expressway in Forest Park, Illinois. It also has two stations on Western Avenue: one on the segment between downtown and O’Hare, and one immediately west of downtown.) The Blue Line also has two in-system transfers (both in the Loop), and does not share tracks with any other 'L' line. Before the adoption of color-coded names, the Blue Line was referred to as the West-Northwest Route, or more commonly, the O'Hare-Congress-Douglas route for its three branches. The Congress and Douglas branches were renamed for their terminals, Forest Park and 54th/Cermak, when the current color naming system was adopted in 1993. Blue Line service on the Douglas segment was replaced in April 2008 by the Pink Line. The Blue Line is one of five 'L' lines that run into Chicago suburbs, with the others being the Green, Purple, Pink, and Yellow lines. The Blue Line runs in three suburbs; Rosemont, Oak Park, and Forest Park. From Wikipedia
