West-Northwest Route car card map, installed in the ad sash inside railcars, dating from 1972.
(aka Milwaukee-Congress-Douglas, aka O'Hare-Congress-Douglas)
For most of their lives, the West Side "L" lines -- the Lake Street Elevated Railroad and the Metropolitan West Side "L" -- terminated all of their trains in the Loop. This practice continued even after crosstown service began in 1913, which linked the routes of the Northwestern and South Side companies.
The Lake Street simply ran most of their trains eastward on the main line, around the Loop, then back out west to the terminal at Forest Park (Loop cut back to Harlem in 1962). Some trains were diverted to the Market Street Stub instead of the Loop, but there were relatively few of these and this ended for good in 1948. All of the Metropolitan "L"'s branches -- the Douglas Park, Garfield Park, Humboldt Park, and Logan Square -- fanned out from Marshfield Junction. Eastbound trains all proceeded from Marshfield to the Loop on the four track mainline. Humboldt and Logan trains actually crossed the Lake Street's tracks at Lake/Paulina and proceeded even farther south to Van Buren to gain access to the Loop. Some trains were diverted to the Wells Street terminal instead of the Loop, but this ceased in 1955.
The first step toward West Side through-routing was taken in February 1951 when the Milwaukee-Dearborn Subway opened and all Logan Square trains were routed directly to the Loop. No longer would northwest side passengers have to go all the way south just to get downtown; direct access could now be had via Milwaukee Avenue and Lake Street. Unfortunately there was still no through-routing though, since Logan Square trains could not continue west of LaSalle/Congress due to the construction of the Congress Street Superhighway and rapid transit line.
Since the aforementioned construction required the demolition of the four track former-Met mainline to the Loop, Garfield Park trains were rerouted onto temporary street level operation over a 2 1/2 mile portion between Sacramento and Aberdeen, with no stops between Halsted and Kedzie, starting September 20, 1953. During this period (1953-1958), A/B skip stop service is abandoned on the Garfield Park Line. On April 4, 1954, Douglas branch trains were rerouted to the Loop via the old Logan Square connector (from the former Marshfield Junction to the former Lake Street Transfer) and the Lake Street route to allow further construction on the Congress Line and the Congress Expressway.
After the opening of the Congress Line on June 22, 1958, that line, along with the Douglas Branch were through routed with the line to Logan Square, via the Milwaukee-Dearborn Subway. This line was known variously as the Milwaukee-Congress-Douglas Line and the West-Northwest Route. A/B skip-stop service was also re-instituted there, with all A trains using the Congress Line (making all stops there) and all B trains running on the Douglas.
On February 1, 1970, Northwest service was extended northwest of Logan Square to Jefferson Park, using the median strip of the Kennedy Expressway. The route was further extended on February 27, 1983 when the first segment of the O'Hare extension opened from Jefferson Park to River Road, with the final extension to O'Hare put into operation September 3, 1984.
This through-routed service remains largely the same today, however, known as the O'Hare-Forest Park-Cermak Line or, more properly, the Blue Line.
West-South Route car card map, installed in the ad sash inside railcars, dating from 1972.
(aka Lake-Dan Ryan)
The next West Side to the through-routed was the Lake Street Line. Previously terminating in the Loop, the line was connected with the newly built Dan Ryan Line in 1969. Starting September 28, 1969, the through route used the Wabash Avenue and Lake Street legs of the Loop Elevated.
The West-South Route lasted until February 21, 1993, when the Dan Ryan Line and the South Side elevated lines "traded places" with their through routes. (For more on this, see the The Lake-Dan Ryan Necessitates More Revisions section of the Loop Operations page.)
(aka Lake-Englewood-Jackson Park)
On February 21, 1993, a new connection opened between the Dan Ryan line and the State Street Subway. Dan Ryan trains are routed through to Howard Street forming the Red Line. This meant that the Lake Street Line needed to be repaired and thus the Englewood and Jackson Park elevated lines, previously linked with the Howard Line, become linked with Lake Street line via the Loop Elevated, forming the Green Line. New destination roller signs on trains and route maps conform to the new color coding system.
On January 9, 1994, the Lake-Englewood-Jackson Park Line closed for an extensive renovation project lasting more than 2 years. A great deal of controversy raged during the two year rehab, including debates over station closings, retention of nighttime "owl" service and the date of reopening. On May 12, 1996, the Green Line reopened, but with the Homan and Halsted Lake Street stations closed. A new station at Laramie and a rehabilitated station at Ashland remained unfinished, opening later in the year. The California/Lake station, closed in the service revision of February 9, 1992, was rebuilt and reopened.