I also couldn't find the original picture but another Minnesota Reflections photograph from around the same period shows that wasn't necessarily an unusual number of streetcars for Superior Street. The Twin Ports by Trolley book notes that "every streetcar line except the isolated Highland Park and Park Point lines funneled through Superior Street." It could be a manipulation of the postcard image but it could also be streetcars running different routes converging on Superior Street and then getting a bit stuck behind each other because there is only one track in each direction and they were using the same stops (the transit principle of "bunching"). And a professional photographer would likely wait for a moment like that.