If you were to visit the nation's masonry forts built during the Fort Knox era, you would see many features common to most of them. One such feature is the casemate, a large enclosed space with a high, arched ceiling and places for cannons to fire through wall openings. All of the nation's major masonry forts built from 1816 to 1867 had at least one level of casemates.
Casemates were first developed in European forts centuries ago. By enclosing cannons within thick walls, casemates protected cannons and the soldiers firing them. But firing large cannons within confined spaces also created safety and structural problems. As a result, cannons were more commonly mounted on rooftops to fire over a fort's outer walls. The French engineer Marc Rene Montalembert improved casemate design in the late 1700s, enabling American engineers to successfully use casemates in new masonry forts.
In addition to providing protection for cannons and soldiers, casemates allowed a fort to have several tiers, thus concentrating the firepower of a single fort. Some forts of the period had three or four tiers of cannons. Fort Knox's design allowed for two tiers - one casemated tier protected 23 cannons along the front wall and smaller cannons planned for a level above.
You will notice that casemates are quite shallow, open in back, and have vents in the ceilings. These features helped disperse smoke and noise from cannon fire. The casemates were not joined structurally to the fort's front wall, allowing the wall to be destroyed and the casemates to remain intact.
Construction of a Casemate
1. Granite piers built
2. Wood frame arch centers constructed
3. Wooden boards nailed to frame
4. Layers of brick and granite facing stone laid on boards and mortared from behind
5. Additional layers of brick laid
6. Arch centers and boards removed
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