The web site for the National Park Service is, as you might expect, http://www.nps.gov. Each park has its own web page that can be accessed from there. Someone who visits the NPS web site as much has I do soon notices a pattern to the addresses for the individual parks. They are of the form http://www.nps.gov/xxxx. For a park with a one-word name, xxxx is the first four letters of the name. For a park with more than one word in the name, xxxx is the first two letters of the first word and the first two letters of the second word.
The address for Glacier National Park, for example, would thus be http://www.nps.gov/glac. Pictured Rocks National Lakeshore would be http://www.nps.gov/piro. With almost 400 units in the system, I would imagine that there are a few duplicates. I do not know the rule for that. I would assume that the National Park would have first priority, followed by National Monument, and so on in some hierarchy. But then what does xxxx become for the losing park? I also do not know the rule if the abbreviation is a naughty word.
It looks like I'll have something to do the next time I want to waste a little time. I suppose the answer is somewhere at the NPS web site, but that would be no fun.