Located in Kentucky, Fort Knox was known as the largest repository of gold bullion in Earth's history, holding over 50 metric tons worth over nine trillion U.S. dollars. With the transition to the New World Economy during the late 22nd century, money became obsolete and was turned into a museum.
As of the 2270s, the facility had a reputation for being impenetrable as no one had ever managed to break into it. This despite there having been one notable event in the previous decade, by a couple Ferengi.
In 2375, while planning a heist of a Borg transwarp coil, Captain Janeway of the USS Voyager used Fort Knox as a metaphor to explain the scale and the level of security around the prize they sought. Some of the staff did not understand what Janeway meant, requiring Tom Paris to explain. In light of this, Captain Janeway named their mission "Operation Fort Knox". (VOY: "Dark Frontier")
- According to the novelization of Star Trek: First Contact, following the Third World War, the gold reserves of Fort Knox had been depleted to the point of nonexistence.