 The Pittsburgh light rail lines are vestigial from the city's streetcar days, and is one of only three light rail systems in the United States that continues to use the Pennsylvania Trolley (broad) gauge rail on its lines instead of .Pittsburgh is one of the few North American cities that have continued to operate light rail systems in an uninterrupted evolution from the first-generation streetcar era, along with Boston, Cleveland, New Orleans, Newark, Philadelphia, San Francisco and Toronto.In the early 1960s, Pittsburgh had the largest surviving streetcar system in the United States, with the privately owned Pittsburgh Railways Company operating more than 600 PCC cars on 41 routes.