The first link in signal500's post is, as he noted, an old list. Frequencies for many park units changed when radio systems were replaced to comply with the federal government's self imposed mandate to convert to narrow band by 1/1/2005. The list also shows a few units that have changed in classification, e.g. Death Valley National Monument was changed to a National Park in 1994.
In addition the list does not explain the frequencies listed so repeater inputs are not distinguished from outputs, and simplex use is not identified. Like many lists, 400 MHz frequencies are shown, but in every case I know of, excluding the trunked system used at Golden Gate NRA, the UHF frequencies are used for remote base station and repeater point to point links. On some of the park units I have official information for, there are some frequencies listed that have never been employed there.
Another trend in National Park Service radio systems is to use more nets than park units used to have. Large National Parks used to have one "park net" that all functions used to share. Now nets for law enforcement (protection rangers as they are called), fire, EMS, maintenance and one for all other functions (administration, interpretation, and resource management) may be used.
I like the quote at the top of the page accessed by the first link "OK, the visitors have arrived, it's time to turn on the waterfall and let the wildlife out" or some such is pretty funny. The best one I came across in my career was in answer to the most often asked question in Sequoia-Kings National Park:
Q: Hey Ranger, where is the tree you drive though? (Yes, there used to be a standing live tree, large enough in diameter that a tunnel was cut out of its base prior to it being included in a National Park. It was the Mariposa Tree, located in Yosemite National Park, which fell over in the awesome storm of February, 1969)
A: Pick any one you want!!