San Francisco is a city located in northern California in the United States. It shares many resemblances and similarities to the main location in TUGS. It (along with New York City) serves as a basis for Bigg City Port.
The Star Tugs' liveries with yellow, red and vertically striped blue and white stacks were a typical American design, used in many traditional and modern items, dating well before the 1920s. This was possibly even being depicted on the tugboats of that era.
Most of the Star Tugs are based on the tugs that roamed the San Francisco waters during the 1920s and '30s.