Even ignoring traffic, you are counting the same park multiple times. Kings Canyon, Sequoia, Yosemite, Lassen Volcanic, Pinnacles is not bad but it's not 8.
https://en.wikipedia.org/wiki/File:NationalParks.forwiki.pdf
https://en.wikipedia.org/wiki/List_of_national_parks_of_the_...
But, Muir Woods is part of Golden Gate National Recreation Area and Point Reyes are not separate parks.