Originally Posted by Viajera
maybe you should buy the National Parks Pass which is $50. It covers the entrance fee for you and your inmediate family (spouse, children and parents ).
www.nps.gov
A donation to the National Parks Foundation will get you AAdvantage Miles (10 miles per dollar), plus a National Parks Pass. I think you need to donate $100 to get the pass, I'm not sure. Details are probably on the AA website.