I have to wonder how this might possibly relate to Native Americans? Especially in light of the pilgrim history boards that were discovered. 1917 was just 10 years after Oklahoma became a state, it was called Indian Territory prior to that [1]. And Indian boarding schools [2], where they tried to wash the "savage" away, were a big thing back then. To this day oklahoma has a very high Native American population and current reservations/nations reflect Indian removal [3] as there are many nations there that did not come from that area.
Either that, or the renovation that covered the boards up took place in December (a theory supported by the calendar drawn on one of the boards), and that just happened to be what was on the boards at the time.
[1] https://en.wikipedia.org/wiki/Indian_Territory
[2] https://en.wikipedia.org/wiki/American_Indian_boarding_schoo...
[3] https://en.wikipedia.org/wiki/Indian_removal
edit - added 3rd citation