That map HAS to date from after the time that the old Rock Island yards were replaced by Civic Center (and the CRI&P station adjacent to the Skirvin abandoned). That would put it in the mid to late 30s. It's also wrong in at least one area; there was never a trolley line on NW 20 -- it was on NW 19 instead. That error, however, might have been deliberate to trap anyone trying to copy the map.