Today I added Yellowstone National Park to the Duckwyn Travel Passport. It's the 7th park to be added to the collection. The park is so vast that you may need to enter the park before you can collect your stamp. Yellowstone has a lot to offer from geysers, to wildlife, to volcanic activity, lakes, and mountains, your family will love the adventure.
According to Wikipedia, there are over 1200 geysers and at least 10,000 thermal features. The 3400 square miles of the park contain hundreds of animal species and over 1700 plant species. Yellowstone is a unique place and beautiful area to explore and get close to nature.