To find the final hiding place of the small container (hopefully still behind a rock), look at the historical sign. It's also a PokeStop; a year from now, will that be relevant?
For the north coordinate, find the date that starts with 16 and look at the two digits after the 16. Subtract 2 from those two digits and flip the digits. Use the answer as AB in N 39 59.4AB
For the west coordinate, find how many thousands of years of Native American culture are represented by archaeological sites in this area. Add that two-digit number of thousands to the last two digits of the posted west coordinates (56) and use those as CD in W 76 28.0CD
Checksum: Digits of last 3 digits of north and west add to 27.
Congratulations to WolfSpirit55 and D.L.Anubis on the FTF after the L.O.S.T. ice cream social.