Providing the basic link, transforming and converting the high voltage alternating current transmitted from the Commonwealth Edison generating stations, to the 600 volts direct current used by Chicago's streetcars and elevated trains.

Converting From AC To DC

Rectifying, or converting alternating current to direct current, was previously a more complicated process. Requiring large rotary converter devices, and substation buildings large enough to accommodate the rotary converters.


In the early 1900's, when the electric railway companies began purchasing electricity from Commonwealth Edison, the newly built substations were owned by the electric railway companies. These buildings housed the transformers and rotary converters, to supply the 600 volts direct current needed for the streetcars and elevated trains. Although at a few locations, the buildings and transformers were owned by Commonwealth Edison, while rotary converters within the buildings were owned by the streetcar companies.

In 1913, the elevated railroad companies began leasing their substations, along with the older generating stations built by them, to Commonwealth Edison. Some of these substations and rotary converters subsequently also provided electricity to streetcar lines, and some street railway substations also provided electricity to the elevated lines. Commonwealth Edison also began equipping some existing and newer substations built by them, with rotary converters owned by Commonwealth Edison. These Commonwealth Edison substations served both streetcars and elevated trains. Many substations were eventually modernized with newer rectifier equipment, or replaced. Finally, CTA assumed ownership of the substations which continue to serve the rapid transit lines.

Many substations historically served both streetcars and elevated trains, regardless of ownership of the substations. Chicago Railways and Chicago City Railway were the largest streetcar companies serving Chicago, with Calumet & South Chicago Railway operating streetcars on Chicago's far south side.

Substations Constructed By Elevated Lines
Substations Constructed By Chicago Railways
Substations Constructed By Chicago City Railway
Commonwealth Edison Substations Serving Calumet & South Chicago Railway
Commonwealth Edison Substations Serving North/West Sides
Commonwealth Edison Substations Serving South Side
Commonwealth Edison Substations Serving Rapid Transit Lines
CTA Substations

As the electric utility serving Chicago, Commonwealth Edison built many substations throughout the city, distributing electricity to the more typical consumers. Most Commonwealth Edison substations were never equipped with the rotary converters, and are beyond the scope of this web page.


Many substations continue in use for the CTA rapid transit, or were more recently replaced with new substations nearby. Some old substation buildings remain standing, adapted for other purposes.

Photos are generally organized by present rapid transit lines, which now are the only present users of direct current from these substations.

Loop Area
Brown Line
Red/Brown Combined Line
Red Line/North
Blue Line
Green Line
Pink Line
Surface Lines Only




Links to substation locations, using Google Maps. Satellite views are also available.

In Chicago, odd address numbers are on the south or east sides of the street, and even address numbers are on the north or west sides of the street. Some substations are not actually located along the named street, but might require walking away from the street through an alley or underneath an elevated structure.

Much information on substations is from the annual reports of the Chicago Traction Board of Supervising Engineers, which provides many details covering the continued modernization of Chicago Surface Lines. No such equivalent resource has been found for the Chicago Rapid Transit, so information is less complete for those substations. But because of the commingling of the power distribution between the streetcar lines and elevated lines, and because the rapid transit system continues to exist, information is available for most rapid transit substations. And any further information would be appreciated. Bill Vandervoort