Use Library Search to find books, government documents, and other library materials owned by or made available through TULibraries. Search by both corporate author, i.e. for the "United States National Park Service" as the corporate author of government documents relating to your park or unit, and by keyword or subject for your particular park. For example, "Yellowstone National Park."
Google is able to crawl/index a great many government information websites. Although results can be hit or miss, you might wish to search Google for your park or unit name AND "enabling legislation" AND site:gov, for example <"mesa verde" "enabling legislation" site:gov>. Sometimes the terms <establishment> and/or <proclamation> can be substituted for "enabling legislation". You might also try substituting site:edu for site:gov. See below for more sample searches.
Note a couple of things about these searches. The first is that Google by default returns websites that contain all search terms. In library databases, as opposed to Google, this is typically ensured by placing the AND operator between search terms. Google also respects phrase searching, which means that you can use quotation marks to force the search engine to return a list of only websites that contain a particular phrase, e.g. "crater lake national park".
For newspaper coverage of your NPS park or unit from the past couple decades (assignment #3) try.:
The United States Government Manual is published annually. It contains information about executive branch agencies including the Department of the Interior and the National Park Service. A researcher might use The U.S. Government Manual to find the names of NPS directors and other officials for a certain presidential administration. The manuals show how the structure and purpose of Interior Department agencies changed over time. Descriptions of agencies sometimes include references to legislative acts and executive orders that can be searched in one of the government documents databases listed on the homepage of this guide.
TULibraries provide access to The United States Government Manual dating all the way back to 1935 both in print (Paley Stacks, call # JK421. A3) and online through HeinOnline via the link above.