As you all know, I love the National Parks and all what's linked to it.
These popular decals were given out at 12 National Parks when the entrance fee was paid, each featuring an animal, hence the term "Zoo Windshields". The stickers were so popular that visitors often asked if they could have an extra one. Due to the popularity of the decals and collections appearing on windshields they reduced the size of the decals in 1923. The use of decals as entrance tickets was discontinued in 1940. Get your own favorite National Park decal here.