Before there were cars there were trains. Between 1908 and 1931, two companies ran interurban trolleys between Pittsburgh and points north. The Pittsburgh and Butler Street Railway operated the Butler Short Line between Pittsburgh and Butler, and the Pittsburgh, Harmony, Butler & New Castle Railway Company operated the Harmony Short Line from Pittsburgh to Evans City where it split and then continued on to Butler and New Castle. The two companies merged in 1917 and became the Pittsburgh, Mars and Butler Railway.
The trolley carried both passengers and freight and was powered by electricity delivered from overhead cables. The cars made frequent stops, although there was a "limited" car that made few stops, and a "party" car for charters.
The rise of the automobile, in particular the bus, and the Great Depression conspired against the trolley. It ceased operating in 1931, and the land was sold and put to other uses. The section that followed Girty's Run out of Millvale was acquired by the county and became Babcock Boulevard.
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http://www.northlandlibrary.org/history/pdf/Harmony%20Line%20article.pdf
Congrats to sgram33 for the FTF!