"I am going to visit all the national parks, and I'm halfway done!"
I can't even begin to tell you how many times I heard this comment as a ranger! And almost always, "halfway done" meant that they had been to 30 or so places. Sigh....
So, what does TheTraveling Ranger mean when he says "national park?" I follow the guidance of the National Park Service, which is that any site managed by the Service that Congress said "will be managed as a unit of the National Park System" (or something similar) is referred to as a national park. That means that national monuments, national historical parks, national seashores, and close to 20 other designations are all "national parks."
Perhaps the most logical way of understanding why a false hierarchy of park names makes no sense is to look at a couple of examples. Grand Canyon was proclaimed a "national monument" in 1908. Its name was changed to Grand Canyon National Park in 1919. What happened that year? Did the Canyon become more grand? Did it suddenly get deeper, or prettier? Did the designated boundaries change? Nope, nope, nope and nope. Run through that scenario for any number of sites: Biscayne, Death Valley, Indiana Dunes, White Sands, Zion. Sometimes they actually DID get larger, but often not appreciably so. So what actually spurred the change? It depends.
Those 20+ different designations really do have subtle differences in meaning. To be a national park, a site has to be nationally significant. How that is determined is in itself pretty loose-goosey! With the 1906 Antiquities Act, Congress gave the President authority to declare any object of "historic and scientific interest" as a National Monument. Any other designation used by the National Park Service requires Congressional approval, so theoretically it has been well-documented and vetted. There are many examples where that did not happen for a variety of reasons, and that will likely be the topic of some future The Traveling Ranger blog post. Oh...and National Monuments can be created by Congress as well.
So if a "National Monument" is a singular nationally significant resource, what is a group of nationally significant resources in close proximity to one another called? THAT is a "National Park," with capital letters.
Because many of the earliest areas designated as "National Parks" were areas of great natural beauty, the idea that national parks HAD to be natural was often assumed, and is still assumed by many today. But Congress made Mesa Verde a National Park in 1906, and its significance is largely cultural.
I can go on and on here, but my point is that there is a great deal of fluidity in naming national parks, and much of that is due to Congressional staffers not understanding the differences in naming conventions. With the exception of "National Recreation Areas (NRA)" and "National Preserves (NPre)" and to some extent "National Seashores (NS)" and "National Lakeshores (NL)," all the units of the National Park System are managed similarly. Extractive uses (hunting, drilling, mining) are generally permitted in National Recreation Areas and Preserves, but never in other units (unless Congress says so....seewhutimean?)
So, in summary, there are 424 national parks. Think of each as a single chapter in a fascinating book called America.