Happy 100th Birthday to the National Park Service on Thursday! To celebrate, everyone gets the gift of free entrance fees to all national parks on August 25th, 26th, 27th and 28th (2016). Fees for camping, lake use or use of concessions still apply.
As an FYI – the two remaining “fee free” days this year will be September 24th in honor of National Public Lands Day and November 11th in honor of Veterans Day!