A free, lifetime pass – available to U.S. citizens or permanent residents of the United States that have been medically determined to have a permanent disability (does not have to be a 100% disability) – that provides admittance to more than 2,000 recreation sites managed by five Federal agencies.
At many sites, the Access Pass provides the pass owner a discount on Expanded Amenity Fees (such as camping, swimming, boat launching, and guided tours).
https://www.nps.gov/subjects/accessibility/interagency-access-pass.htm