Guess what? I found an admittedly very loose connection to the above poster!

Leslie asked from when it may be, which set me off to google.
I found
this page on Wikimedia saying it's from ca. 1937 and was a work done for the
WPA under the New Deal.
And this, which is of course the Riverton post office mural, is also a New Deal piece of art (from 1942).

Ta-da!

ETA: Oh my, once you start googling, you can really get lost!

Slightly OT:
Did you know that Ennis and Jack had a second job as excavators?

Down in Kemmerer, WY. Near Sage, where Ennis came from.

Mural in the post office of Kemmerer, WYSorry for the OT.