As Johnson notes, the two largest systems, in Philadelphia and New Orleans, are upgraded versions of original streetcar lines that have been in place for more than a century. This map doesn’t include San Francisco’s Muni Metro system or Boston’s Green Line; both are descendents of historic systems, Johnson says, but today they operate more as light rail lines. This image also doesn’t include tourist-oriented lines with limited hours of operation, such as Savannah’s River Street Streetcar.
