Voronoi Map of National Parks: the USA divided into regions based on which national park is closest. There are 59 national parks in the US.
Love America the Beautiful? Get out there and see it. (doubleclick for huuuge):
Relephant comments: There are probably hundreds more lesser known parks/reserves/monuments managed by the NPS. You can view the listings on their website. And please explore the National Parks near you.
“And if you really want to get things confused start looking at Wilderness Areas. These can exist in National Parks, National Forests, BLM land, and Fish and Wildlife Service land. There’s 757 of them right now. They’re almost completely unmanaged other than trail maintenance. No vehicles allowed, etc. I’ve visited a few and they’re generally amazing. Most people don’t really know about them or what they entail.”
On the other hand: