Streetcars and trolleys were the primary mode of transit, but with the onset of the combustion engine, automobiles, and buses emerged a new mode of public transit. Initially dubbed “trackless trolleys” in a marketing pitch to get people to switch, they started their assault on the streetcar system and eventually took over most major metropolitan cities in the U.S. by the 1960s.

Check out this cool vest pocket guide for the Baltimore bus system from 1938.