Fossil Cycad National Monument was a national monument in the U.S. state of South Dakota beginning in 1922. The site contained hundreds of fossil cycads, one of the world's greatest concentrations. Because vandals stole or destroyed all of the visible fossils, it was withdrawn as a national monument in 1957.
A fuller story is available here: Fossil Cycad National Monument: A Case of Paleontological Resource Mismanagement.
If the NPS don't sell these posters to fund the protection of other parks then they should. The image is at the NPS site here and it says: Commemorative artwork for Fossil Cycad National Monument 1922 - 1957. NPS image.