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 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
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.
Photos are generally organized by present rapid transit lines, which now are the only present users of direct current from these substations.
Red/Brown Combined Line
Surface Lines Only
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.