The National Parks will offer free entrance to over 127 parks that usually charge from April 16 - 24.
In North Carolina, you can enjoy the Wright Brothers National Memorial at no charge during the free entrance days. For all the information about this promotion including locations in North Carolina, see the National Parks website.
The website points out that over 273 national parks never charge an entrance fee at all!
Additional 2016 free entrance days include:
August 25 through 28: National Park Service Birthday
September 24: National Public Lands Day
November 11: Veterans Day