<P> The O'Hare Branch is the longest section of the Blue Line ( 14.6 miles ( 23.5 km ) ) and comprises both the oldest and newest segments of the entire route . The line starts at O'Hare International Airport in an underground station below the main parking garage , servicing Terminals 1 , 2 , and 3 . The line emerges in the median of the O'Hare main access road ( Interstate 190 ) just northwest of Terminal 5 , about a mile ( 1.6 km ) west of Mannheim Road . The line runs in the median of Interstate 190 east through Rosemont . The line has a stop at River Road in Rosemont , which is also the location of one of the line 's two storage yards , then tunnels beneath the Kennedy Expressway / Northwest Tollway interchange near the Des Plaines River . The line runs in the median of the Kennedy Expressway ( Interstate 90 ) until a point southeast of Addison Street . South of Addison Street , the line exits the freeway and enters a subway under Kimball Avenue . The line travels under Kimball Avenue and Milwaukee Avenues through Logan Square . South of Logan Square , the line emerges above ground onto an elevated structure parallel to Milwaukee Avenue . This section of structure , built in 1895 as part of the Metropolitan Elevated 's Northwest Branch , is the oldest portion of the Blue Line , and the sole section of the line on an elevated viaduct . The three stations on this section ( California Avenue , Western Avenue , and Damen Avenue ) are also the only three stations on the line to use side platforms instead of island platforms . </P>
where does the blue line end at o'hare
in an underground station below the main parking garage