The Blue Line is a 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, nine in the Milwaukee–Dearborn subway and 13 on the O'Hare branch). It is the longest line on the "L" system and second busiest, with an average of 186,796 passengers boarding each weekday in September 2012.