The NPS, the National Park Service, provides information for all parks on the websites of the park. They are developing a strategic plan to improve accessibility in all parks for people with disabilities. More information, plus the opportunity to give feedback you find here.
– American citizens or permanent residents of 62 years or older can obtain an Access Pass. This pass costs 80 US dollar and is a lifetime pass.
– 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.
Read more here on several parks with boardwalks to enjoy the best views.