Does 1 purchase of National Park admission grant all admission to all national parks?
In general, an admission fee to a national park only gets you in that park. Usually good for about 7 days. This does vary a little. Check the website of the park(s) you're interested in. If you're planning to go to 3 or more parks in a year, get the America The Beautiful pass at the entry station of the first park you go to. It's $80 and good for a year for everyone in the car. It's valid at almost all parks, monuments, and federal recreational lands.