After World War II, seven major North American cities (Boston, Newark, New Orleans, Philadelphia, Pittsburgh, San Francisco, and Toronto) continued to operate large streetcar systems. Some of these cities called their modernized systems light rail in an attempt to differentiate it from their existing streetcars particularly cities that continued to operate both the old and new systems. Cleveland, Ohio, maintained an interurban system (e.g. the Blue and Green Lines) that is equivalent to what is now "light rail", which opened before World War I, and which is still in operation to this day.