The best known national parks remain extremely popular. Great Smoky Mountains National Park in North Carolina and Tennessee received more than 11 million visitors last year. Grand Canyon National Park in Arizona received more than 5.9 million visitors, and Yosemite in California had more than 5 million. Rocky Mountain National Park in Colorado and Zion in Utah round out the top five parks.
The park service's birthday celebration is an opportunity to get out and explore the landscape, discover historic sites and learn the important role that wildlife plays in our ecosystem. You can also enjoy outdoor activities like camping, hiking and kayaking during the last days of summer.
The service also will help you find a park and plan your visit at its Find a Park site.
And if you miss the Aug. 25 celebration, there will be a few more days this year when admission will be waived. Entrance is free Sept. 30 for National Public Lands Day and Nov. 11-12 for Veterans Day weekend.