The Milwaukee–Dearborn subway is an underground section of the Chicago "L" system in The Loop, Chicago, Illinois. It is 3.85 mi (6.20 km) long and forms the central part of the Blue Line. As of February 2013, the subway serves an average of 44,584 passengers each weekday. Since the subway is served by the Blue Line, it is open to passengers 24 hours a day and 365 days a year.