The Pittsburgh Light Rail is a direct descendant of the Pittsburgh streetcar network, which was at one time the largest streetcar system in the United States. Following the Port Authority's acquisition of the Pittsburgh Railways Company and about 30 other private transportation companies, streetcar lines were converted to bus operations. In the mid-1970s, the Port Authority proposed eliminating the remaining streetcar lines in favor of a bus rapid transit system. However, community objections in the South Hills neighborhoods resulted in the streetcar line being rebuilt as a modern light rail line in the 1980s. Light Rail service began in 1984, and a subway section was constructed in Downtown Pittsburgh and opened in 1985.

Today, the Pittsburgh Light Rail has two lines serving 53 stations along 26.2 miles of track. About 27,700 people use the light rail each day as of late 2014.