I found this very "Rare" and historic early 1950's era photo from the Chicago Transit Authority at My Link page Tom's Trolleybus Pictures, located to the right of Your computer screen at www.trolleybuses.net

The Chicago Transit Authority was formed in the year of 1945, but did not begin operations until November 1st, 1947.

The CTA, was focused early on to replace the electric streetcars with motor buses.
Between 1947 and 1955, the CTA converted several former or soon to be former electric streetcar routes. to electric trolleybus operation. With the overhead wires and electrical substations already in place, it was economical at the time...to just add an extra overhead wire. The trolleybuses operated on 600 Volts DC just like the electric streetcars did.

This photo was taken somewhere on West Irving Park Road during May of 1953. Irving Park Road, was still using standard double ended electric streetcars from the early 1900's era, but this route would soon be converted 100 percent to electric trolleybus operation.

This is a "Rare" transitional photo, of a streetcar line being converted to electric trolleybus operation in Chicago Illinois USA.