There is a variety of information available on the history and mission of the National Park Service that might be helpful in planning lessons.
The National Park Service website has hundreds of publications on the history of the National Park Service and a variety of information on how the system works and its mission.
Many parks around the system also have lesson plans and other information online, allowing students and teachers to explore the park system from the classroom. Lesson plans, education guides and general information for educators on history topics.
If you would like to learn more about the establishment and history of Nez Perce National Historical Park and Big Hole National Battlefield, there are administrative histories available here: