CTA Blue Line - Expansion - Stub Tunnels

Stub Tunnels

The dual portals of the Congress Branch at UIC-Halsted are actually quadruple; two extra portals also exist to the north of the Blue Line portals, which extend only a few hundred feet beyond the portals, These were intended to accommodate future expansion, including a new CA&E line to a new terminal, or for a variety of later CTA new line proposals which were never realized. Among those plans were a loop subway system via Congress, Dearborn, Lake, and Clinton when the Milwaukee-Dearborn-Congress Subway was completed between 1951–58; a shuttle subway route under Jackson Street to Grant Park (1958 New Horizons for Chicago Metropolitan Area, CTA); and more recently between 1968-78 in the form the Distributor Subway system which was to be routed from UIC-Halsted Station through the north portals, then north under Desplaines Street to Monroe Street, and east under Monroe Street to Grant and Millennium Park where it was to split into two branches: one north to Walton Street serving the North Michigan Avenue area and the other southeast to McCormick Place utilizing Metra Electric right-of-way. Though these portals are still not used, the Monroe Street Distributor Subway was never "officially" cancelled when the Crosstown and Loop Subway projects were deferred in 1979. It remains to this day an active program.

Between Grand/Milwaukee and Clark/Lake in the Milwaukee-Dearborn Subway, two more stub tunnels also exist, continuing straight while the current Blue Line heads in the northwest direction. This flying junction (actually a stacked flying junction), built in the 1940s along with the initial subway, was intended for a never-built connection to, or subway replacement of, the Lake Street Elevated. In the late 1960s through the mid-1970s, they were also proposed to be a service link between the Dearborn Subway and a high-speed subway route in Randolph Street to replace a portion of the Lake Street 'L' east of Damen Avenue (Transit Planning Study Chicago Central Area, April 1968).