I can't find any record of a Cassius Street in Pittsburgh. I have looked at historic maps with no luck. Could it be mislabeled?
I found Cassius Street on Volume 2, Plate 4 of the 1939 G.M. Hopkins & Co. Map. The link is too long but you can search for it at http://digital.library.pitt.edu/map....
It's just a narrow alleyway between Shakespeare St. and Aurelia St. The Shakespeare St. Giant Eagle is right on top of that location now.
Bob- The links get truncated by the comments field. but they still work.
Bob, thank you for finding this one. I've known about this picture for months and its location has been a mystery.