“National Park” has a very specific definition for the Dept of the Interior, the government agency that governs them. National Seashores, National Historical Sites and Parks, and National Memorials are often wonderful places, but they are not National Parks as the DoI defines them. https://en.wikipedia.org/wiki/List_of_national_parks_of_the_United_States
As the Wiki puts it: “Other units of the National Park Service are sometimes incorrectly referred to as national parks; they are listed here.”
My natal state of NJ is full of National Historical Sites that don’t meet the qualifications of a National Park. In northern NJ, you can’t throw a stick without hitting one. I’ve always enjoyed Fort Nonsense which may or may not have actually ever existed.
