The view along Fort Jefferson's southeast curtain wall. Its lovely moat, while seemingly a pointless extravagance for a fort already surrounded by water, protected it from direct exposure to the ever-lapping sea...and also served as yet another obstacle for an attacker. Imagine the Spanish Navy receiving orders to take Fort Jefferson in 1898, and sailing halfway around the world to do so, only to find that they had to cross another several yards of water! Surely they would have thrown up their hands and returned home.

Fort Jefferson's moat was mostly built from 1849 to 1851, but did not attain its final depth until 1873, when there were plenty of prisoners on hand to do the digging. I learned this by reading one of the fort's many informational signs: The Moat.