The National Park Service is celebrating its centennial, and we couldn't be more grateful for the agency's work to preserve "unimpaired the natural and cultural resources and values" of America's national parks. To celebrate, a photo of the always stunning Yellowstone Park, the first national park in the country. Happy birthday!
Would you like to see your nature photo featured as the TreeHugger photo of the day? Join TreeHugger’s Reader Photo Pool on flickr and add your pictures to the group.