I read about this place in grade school and it sounded otherworldly in a perverse, medieval way. But it is so remotely located that visiting seemed just too much time and travel, but then Vivien and Bill wanted to see it on their annual week visit with us. As with many such things, you only go see the neat stuff nearby when you have guests.
The US Navy scouted the place just after acquisition looking for a base from which to counter pirates in the Caribbean, but judged the group of low, sandy islands unfit for a structure.
But it was later argued that the Dry Tortugas -- so-called because they were generally dry and often held populations of turtles, at least in Spanish days -- were too strategic for the US not to fortify, lest some other power do so.