I grew up in Pittsburgh Pennsylvania. The Pittsburgh Railway company was owned by Andrew Carnegie’s empire. An important aspect of the streetcar system was that it allowed the workers to get to his steel factories.
This map was for sale at what originally was called the Arden trolley museum. It went from being a non-profit organization to a museum operated by the state of Pennsylvania. I scanned this a very long time ago, and then created a KML file for Google Earth that showed all of the routes and to the extent possible where they ran.