CTA POWER DISTRIBUTION
The streetcars were originally powered by horses, and the elevated trains were originally powered by steam locomotives. In the 1890's as electric power proved to be practical, the railways constructed their own power generating stations. In the early 1900's, the individual generating stations were replaced with the more efficient central power generation of the area electric utility, Commonwealth Edison.
Chicago's street railways and elevated railways largely have separate histories, and are treated separately throughout most of this web site. But as Commonwealth Edison evolved as the supplier of electricity to both systems, much of the electrical distribution system became commingled. With many substations converting the electricity to 600 volts DC for both systems. Electric powered surface transportation existed until 1973, in the form of trolleybuses. But a few substations originally constructed by the street railways, continue to be in use for rapid transit trains.
Between 1882 and 1906, Chicago had what once was the world's largest cable car system, for the heaviest streetcar routes. The cable cars were powered from stationary steam engines located at several power houses.
Electric generating stations constructed by the streetcar companies during the 1890's, providing the 600 volts DC to the streetcar lines.
Electric generating stations constructed by the elevated railroad companies during the 1890's, providing the 600 volts DC to the elevated lines.
In the early 1900's, when the electric railways transitioned to the purchase of electricity from Commonwealth Edison, substations were established for the distribution of direct current electricity to the overhead wires and the third rails.
Between 1903 and 1912, Commonwealth Edison opened three large coal fired generating stations, serving all of Chicago's electricity needs including for the streetcars and elevated trains. But public transportation continued to be the most significant early user of electricity, in 1908 still accounting for 65 percent of electricity usage.
Much information on older transit facilities is from the "Sanborn Fire Insurance Maps", which is a fascinating and valuable resource in determining exactly what buildings were where, historically. People with a Chicago Public Library card can access these maps online at the Chicago Public Library Web site. Because the map collection is incomplete, not all older transit facilities are known, and any further information would be appreciated. Bill Vandervoort