The National Park Service (NPS) has long encouraged visitors to avoid peak crowds by planning their trips in the spring. And to give you even more impetus, here’s another good reason to visit this month: free admission.

AARP News reported that for four days in April — April 15, 16, 22 and 23 — the National Park Service will waive entrance fees at the 118 national parks that normally charge visitors. The fee-free days are all part of National Park Week, which is celebrated from April 15-23. In total, 10 free days are offered in 2017. After April, the other fee-free days are Aug. 25, Sept. 30, and Nov. 11 and 12.

Entrance fees, commercial tour fees and transportation entrance fees are all included in the fee waiver. Other charges, such as those for camping, tours and concessions collected by third parties, are generally not included.

Park officials say the fee-free days are designed to make sites accessible to a broader group of people.

In addition to the highly popular sites such as YosemiteYellowstone and the Grand Canyon, there are plenty of lesser-known parks to check out including Congaree in South Carolina, Dry Tortugas in Florida, and North Cascades in Washington.

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