The Tacoma Municipal Street Railway -- Tacoma Belt Line Railway after 1925 -- operated electric trolleys to move people and electric locomotives to move freight. As the switching business grew and the passenger business shrank, the trolleys interfered with locomotives. In 1920, the system had 38 streetcars. Ten years later it had nine streetcars and two small buses. The 11th Street Bridge carried streetcars from downtown to the tideflats, but in 1929 the bridge burned down. Two 18-passenger buses were purchased to fill that gap. Buses did not require rails and could be given new routes without the need to construct tracks and wires.
In May 1938, the Belt Line replaced the streetcars with buses built by Tacoma’s White Company. The shift to buses did not improve the Belt Line’s profitability, even during the industrial boom of World War II, despite carrying 17 million passengers between 1941 and 1945. At the end of the war, the City Council, faced with replacing the entire fleet of buses, voted to turn passenger operations over to Tacoma Transit Co.