I see, did you also know that 6 national parks in Alaska and 1 other are paired with national preserves?  The areas have different protection levels but administered together.
You'd probably have to travel across the entire continental US, and then to Alaska because six national parks are there alone!
Have you ever visited Yellowstone National Park? It's a cool place! I haven't but it was the first national park signed into law through President Ulysses S. Grant during 1872. That's very true. Tedy Roosevelt also had a lot to do with National Parks too  I believe. I didn't know Ted Roosevelt was involved, but I do know that the US has 59 national parks that the National Park Service operates in. Yeah I think it would be really cool to visit them all but that's a lot of ground to cover!
Seven national parks (including six in Alaska) are paired with a national preserve, areas with different levels of protection that are administered together but considered separate units and whose areas are not included in the figures below.