The demand for fast passenger service between Chicago and the Twin Cities quickly outstripped what the original Twin Zephyrs of 1935 were able to supply. New equipment with a much higher passenger capacity and all the luxury touches passengers could expect for daytime travel was ordered and entered service on December 18, 1936. It appears as if the capacity may have been bumped upward yet another notch by the time of this schedule; the reference material I have available (Schafer/Welsh; Classic American Streamliners) states that the new trains had two full coaches each, but the equipment listing in the September 1938 Guide clearly states that there were three!