Official Web site of Port Authority Transit.
In 1964, the Port Authority of Allegheny County became responsible for all public transportation in the Pittsburgh area. One streetcar line continues to operate, although mostly on private right of way.
Several individual streetcar companies were eventually consolidated into a single company, prior to conversion to buses.
How the electric railways and private bus companies evolved into today's bus system.
Prior to the public takeover and unification, 29 independent private bus companies operated in Pittsburgh's suburbs.
Map showing connecting electric railways of the past, allowing for continuous journeys beyond Pittsburgh into southwestern Pennsylvania.
Jon Bell's Rail Transit Pages/Pittsburgh
Port Authority Transit (Wikipedia)
Antique Motor Coach Association of Pennsylvania
Information from various sources, including various issues of the magazine "Motor Coach Age", the Poor's and the Moody investment manuals, and "The Trolley And Interurban Directory", by Joseph Gross.
Chicago Transit & Railfan Web Site