The Pittsburgh, Harmony, Butler and New Castle Railway, commonly called the Harmony Line, was a broad gauge interurban streetcar line connecting Pittsburgh, Pennsylvania, United States to Butler and New Castle via Harmony and a split at Evans City. There was also an extension that was later added to the line from Ellwood City to Beaver Falls.

Butler is a city and the county seat of Butler County, Pennsylvania, United States. It is located 35 miles (56 km) north of Pittsburgh and is part of the Greater Pittsburgh region. As of the 2020 census, the city population was 13,502.