Foamer Special:

 

An outstanding photo of Loewy's Pennsylvania Railroad S1 and one of the Dreyfuss Hudson’s. They were the epitome of railroad design at the time.

I'm informed that this 'race' HAD to have occurred on the mainline leaving Chicago, because that was the only place their tracks ran parallel long enough to really roll.
However these two appear to be at rest, from the nearly vertical plume of smoke from the S1.