Fort Knox was built to face British guns. But it never did. In fact, it never faced guns at all.
The British Royal Navy had roamed American rivers and ravaged American coasts during the Revolution and the War of 1812. In the early 19th century, planners decided new forts could prevent this. Fort Knox, for example, would be planted on a hillside in Prospect to loom over a narrow channel in the Penobscot River. From there, it could rain fire on enemy warships and stop them from attacking settlements upstream.
Money for the fort was slow in coming. So construction slowed, too. Soldiers arrived at Fort Knox during the Civil War to find builders still working on the massive, brick and granite structure. Construction was finally halted in 1869. The job was never finished.
Decades later, troops briefly garrisoned Fort Knox again, this time during the Spanish-American War. Finally, in 1923, the fort was closed and sold to the State of Maine.
No enemy fleet had ever challenged it.
Today, visitors can tour the old fort, now the Fort Knox State Historic Site. Inside, they can wander shadowy passageways and batteries and examine its massive Rodman cannon.