Downriver and River Thunder by Will Hobbs (Grand Canyon), Frozen Stiff by Sherry Shahan (Denali), the Roland Smith I,Q series all take place at National Historic Sites or end up there.
I noticed that most of the major books on parks are on Western parks. I think you need to remember anything taking place in Philadelphia around Independence Hall, the Liberty Bell, etc. would be considered a National Historic Park. Same with Washington, D.C. Mall area. Gettysburg and other National battlefields such as Shiloh.
I really suggest you send for or look up on the NPS site the list of all National Parks, sites, monuments, waterways, etc. There are probably a lot more books out there than you may think.