3 years earlier, Chicago Surface Lines had introduced its first trolleybus routes on the Northwest side. And some gasoline bus service had been introduced. And the Chicago Motor Coach Company (CMC) was operating over Chicago's boulevards.

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

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 buses in parentheses, CMC buses in brackets.

Red circles indicate CSL streetcar barns, brown circles indicate CMC bus garages. In addition, Elston Ave. and North Ave. housed trolleybuses, and 77th St. and North Ave. housed gasoline buses, as indicated by their multicolored circles.

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