The service was descendant of a Key System streetcar and ferry line that operated prior to the formation of AC Transit.

[2] Local shuttle service was retained with two-axle "dinky" streetcars as a term of the old 40th Street charter.

Starting on November 21, 1924, the line was extended along existing streetcar tracks on Piedmont, running north to Grand to enter the right of way of the company's abandoned San Jose interurban line as far as Oakland Avenue adjacent to Latham Street.

[4][5] Partial bus replacement commenced in May 1931 as part of a cost cutting measure and conversion to one-man operation.

[6] Cars began running across the San Francisco–Oakland Bay Bridge to the Transbay Terminal upon the facility's opening in 1939.