Entrance to all 392 national parks is free during National Park Week, April 18-25.
Parks will also offer additional family-friendly activities and special offers on tours, lodging, food, and souvenirs. Visit the Web site for a listing of parks and promotions. There will be hundreds of family friendly events on Saturday, April 24, for National Junior Ranger Day. Each child participating in Junior Ranger activities will receive a certificate, patch, or pin. Other National Park Week highlights include the 40th anniversary of Earth Day and the 75th anniversary of the nation’s most visited national park – the Blue Ridge Parkway. Normally, 146 of 392 national parks charge entrance fees ranging from $3 to $25. The other 246 do not charge for admission.
The fee free waiver for National Park Week does not include other fees such as fees charged for camping, reservations and concessions.
Here is a link for National Park locator.