The first US stamp to depict the Stars and Stripes on the moon was the 10c airmail stamp (Scott C76) issued on September 9, 1969, to commemorate the successful moon landing of Apollo 11 and crew Neil Armstrong, Col. Edwin “Buzz” Aldrin Jr., and Lt.Col. Michael Collins.
Created by artist Paul Calle, the stamp was printed from a master die carried to the moon, in the lunar module “Eagle.” The flag of course, is a patch on the left shoulder of astronaut Neil Armstrong. In the years to come, there would be many more “moon stamps” prominently showing the flag, but this was the first.
The first US flag on the moon was probably on the lunar module Eagle itself, but I will need to research that and see if I can find photos from all sides of the module.
Writer George Amrick details the story of this first “moon landing” stamp, and others, at www.unicover.com. It is a fascinating story and I hope you will take the time to link over and read it.