National Park Service windshield stickers

In the 1920s and 1930s the “must have” souvenirs weren’t created to be collected at all. National Park Service windshield stickers served a practical administrative purpose; they were evidence that the automobile license fees due at some parks had been paid. Americans embraced the stickers' colorful, artistic designs, sparking a collecting craze. Drivers pasted so many to their windshields they quickly became a safety hazard.

https://www.nps.gov/articles/000/50-nifty-finds-18-portable-posters.htm

https://www.cbsnews.com/pictures/national-park-service-centennial-early-vintage-photos/10/

https://www.nationalparkstraveler.org/2010/06/wouldnt-it-be-nice-if-national-park-service-resumed-distribution-park-window-stickers6063

https://justacarguy.blogspot.com/2022/09/ill-be-darned-i-didnt-know-there-were.html

https://www.shorpy.com/node/19904?size=_original#caption