Those I have been to:
North Cascades Nat Park,WA--Mt Baker's Artists Point
Olympic Nat Park,WA--Hurricane Ridge
Mt Rainier Nat Park, WA--I have hiked most of the trails here.
Mt Saint Helens Volcanic Monument,WA
Crater Lake Nat Park, OR--Wizard Island
Death Valley Nat Park, CA--Date Palms near golf course
Teddy Roosevelt Nat Park, ND--North Unit
Petrified Forest Nat Park and Painted Desert,AZ
Grand Canyon Nat Park,AZ--South Rim
Zion Nat Park, UT
There are also several Nat Monuments and as a kid with my parents there was Craters of the Moon, Redwoods, and Yellowstone.