If manmade lowest points like Winnrock Quarry are accepted, is the same true for highest points? Are the highest points in (naturally) low-lying states the tops of skyscrapers? If someone constructed a 70-ft tower on top of Mount Elbert, would Colorado wrest the lower-48 highpoint trophy from California?
Tough call. Buildings and human-disturbed land are not considered part of a high point. Might be splitting hairs, but the lowest point is still natural land, it's just the land on top was removed.