Part of a series on underground Chicago.
Subway Tunnels: 11.4 miles
CTA’s rapid transit system has two lines in tunnels underneath the central area. The Blue line is also underground between Logan Square and Belmont and at O’Hare. Small portions of the system are underground elsewhere. One unique structure on the Green line is a tunnel, yet above ground.
Freight Tunnels: 60 miles, 7.5 feet high, 40 feet down
In 1899, construction began on what was supposed to be wire conduits for a telephone system. The enterprise soon turned into a narrow gauge freight railroad. Hidden from sight, the builders felt little need to consult the city or anybody else about the exact route. They just dug madly by hand until ultimately the system was under every Loop street. If you had a Loop business one day they would come knocking on your subbasement door (which you didn’t know you had) and announce “you have freight service.” Rail operations ceased in 1959 and the tunnels reverted to the city. The tunnels have been repurposed to their original role of wire conduits. They famously flooded in 1991.
Street Car Tunnels: Almost a mile in total length.
Among Chicago’s oldest tunnels are the three tunnels under the Chicago River. They were rebuilt in the early 1900s, and served street cars until 1959. Currently they are unused, but intact.