The next free day is Saturday, Sept. 27, to celebrate National Public Lands Day.
The annual celebration falls on the fourth Saturday of September and has been the nation’s largest single-day volunteer effort since 1994. Last year, more than 130 national parks hosted events with 7,600 volunteers donating 41,500 hours of service.
A list of volunteer events at the national parks is available here.
The parks will also waive entrance fees Oct. 12 and Nov. 11 this year.
