Official Web site of the Tri-County Metropolitan Transportation District of Oregon.
In 1969, Tri-Met became responsible for all public transportation in the Portland area, acquiring the Rose City Transit Co. In 1970, Tri-Met acquired the Blue Bus Lines, operating in the suburbs. The last streetcars ran in 1950, and trolleybuses operated from 1936 to 1958. And a new light rail system began operating in 1986.
Several individual streetcar companies were eventually consolidated into a single company, prior to conversion to buses.
How the electric railways and early bus operations evolved into today's bus routes.
Information from various sources, including the September 1971 issue of the magazine "Motor Coach Age", and the book "Fares, Please! Those Portland Trolley Years", by John T. Labbe.
Chicago Transit & Railfan Web Site