The Chicago Surface Lines is taken over by the CTA. Newer transit routes were using buses, and a few streetcar routes had been converted to buses. The Chicago Motor Coach Company (CMC) continued to operate independently.

The following colors are used to indicate types of routes:
RED - streetcars
BLUE - trolleybuses
GREEN - CSL gasoline and diesel buses
BROWN - CMC bus routes

Red circles indicate CSL/CTA streetcar barns, green circles indicate CSL/CTA bus garages, and brown circles indicate CMC bus garages. In addition, Elston Ave. and North Ave. housed trolleybuses, and North Ave. and several other streetcar barns housed gasoline and diesel buses, as indicated by their multicolored circles.

At the time, numbers were used to identify bus routes, while streetcar route numbers were generally not used publically. Bus route numbers are indicated, CSL/CTA buses in parentheses, CMC buses in brackets.

Separate panels show transit routes on Chicago's north and south sides.

Not shown are express bus routes, along with downtown shuttle routes and downtown routings.