Great news!  Another original of Grand Canyon National Park turned up in Sedona AZ and was donated to the park.  It came out of the estate of a Librarian who worked for the park beginning in 1951, about the time the US Mint building was closed and the posters stored there (during WWII) were returned to their parks.  This one is a bit faded which puzzled me as other duplicates with similar exposure to light do not show fading.  This is the 42 confirmed original and fifth Grand Canyon.  Of the 14 designs made, I’ve found 12 (still missing are Wind Cave and Great Smoky Mountains).  One Yosemite turned up 10 years ago but slipped through my fingers (and those of the Library of Congress) so three are missing from the public domain.  I’ll offer a $5000 reward for each of these with the promise to donate to the NPS archives at Harpers Ferry.