According to the National Park Service, many of the more than 400 national parks never charge an entrance fee. The fee-free days apply at the 124 national parks that usually charge entrance fees.
Click here for some ideas of amazing places that will thrill.
* “Fee waiver includes: entrance fees, commercial tour fees, and transportation entrance fees. Other fees such as reservation, camping, tours, concession and fees collected by third parties are not included unless stated otherwise.”