The National Park Service (NPS) website consists of thousands of individual pages. The two most helpful areas of NPS.gov for assignments #1 and #2, respectively, are the published Laws Relating to the National Park Service; and the administrative histories of many parks, units, monuments, and other NPS-manages sites.
From the National Park Service (NPS) homepage, try clicking Find a Park > by name > Management > Laws & Policies > Enabling Legislation [if available].
A convenient list of Yosemite's enabling legislation beginning in 1864 and running through 2013 can be found here. Uncovering the legislative histories of other parks and NPS units can be a bit more challenging. Explore the other boxes on this guide for more tips on how to find the enabling legislation for other parks.