The party must be over in 2017. The number of entrance fee-free days in the National Park System is dropping by 40 percent, to just 10 from the 16 you could have taken advantage of this year. Gone are the weeklong free days during National Park Week in April, and a long fee-free weekend in August to celebrate the founding of the National Park Service. 

The National Park Service's birthday, August 25, falls on a Friday, which would seem to make it the perfect kickoff for a three-day free weekend in the parks. But fees will only be waved on August 25. And National Park Week has been reduced to National Park "Weekends."

"Last year, we added extra fee-free days for the centennial," said Park Service spokeswoman Kathy Kupper. "We had 16 fee-free days in '16. Most years, we've had around nine. The additional days last year came from adding extra fee-free days to National Park Week and the birthday."

The fee-free days scheduled for next year are:

• January 16: Martin Luther King Jr. Day
• February 20: Presidents Day
• April 15-16 & April 22-23: National Park Week weekends
• August 25: National Park Service birthday
• September 30: National Public Lands Day
• November 11-12: Veterans Day weekend

“National parks are known for their priceless beauty,” said National Park Service Director Jonathan B. Jarvis in a release announcing the dates. “They are a bargain anytime, but on these 10 days in 2017, they really will be priceless. We want everyone to visit their national parks, and the fee-free days provide extra incentive to experience these amazing places.”

During the fee-free days, all National Park Service sites will waive their entrance fees for all visitors. Usually, 124 of the 413 national parks charge entrance fees that range from $3 to $30. The other 289 sites do not have entrance fees. The entrance fee waiver for the fee-free days does not cover amenity or user fees for things such as camping, boat launches, transportation, or special tours.

To continue the national park adventure beyond these fee-free days, the annual $80 America the Beautiful National Parks and Federal Recreation Lands Pass allows unlimited entrance to more than 2,000 federal recreation areas, including all national parks. There are also free or discounted passes available for senior citizens, current military members, fourth-grade students, and disabled citizens.

The National Park System includes more than 84 million acres and is comprised of 413 sites including national parks, national historical parks, national monuments, national recreation areas, national battlefields, and national seashores. There is at least one national park in every state.

Last year, 307 million people visited a national park. They spent $16.9 billion, which supported 295,000 jobs and had a $32 billion impact on the U.S. economy.

In addition to national parks, the National Park Service works with tribes, local governments, and partners across the country to help preserve local history and create close-to-home recreational opportunities. Programs such as the National Register of Historic Places, National Heritage Areas, National Wild and Scenic Rivers, and the Rivers, Trails, Conservation Assistance Program revitalize communities, celebrate local heritage, and provide places for people to get outside, be active, and have fun.