Southern? Well, kinda sorta
Interesting. I don't know if this kid from Columbia University thought his answer was right ("this southern national park is the largest one entirely within one state") or just couldn't come up with the right one. But his answer - Yosemite - was startling to me, because I don't think of California - even southern California, which Yosemite isn't in (it's in eastern central California) - as "southern". Sure, it's not up by Canada, but "southern" in the US doesn't even include border areas of Arizona or New Mexico. It's a pretty specific area, less geographic than historical and cultural.
But maybe the college kids think differently?
(The answer was the Everglades, of course.)