the people and all the taxpayers in this country. MLK day is observed by government agencies, public schools and Wall Street. Only those people working for those employers enjoy a day off and have a chance to get a free admission to national park. But national park services is funded by all taxpayers. If you want to be fair, you need to choose a holiday observed by most taxpayers, e.g. like Ned mentioned, Labor Day to offer free admission to national parks.