Fort Sumter's powder was stored in these specially constructed rooms in the corner (angle) of the gorge wall. Protecting gunpowder was critical; the gorge, at the rear of the fort, was considered a safe location. But Fort Sumter was designed to face the sea, and was vulnerable to attack from land. When Confederate batteries bombarded the fort in April 1861, the resulting fire threatened the magazine, causing Major Robert Anderson to surrender rather than endanger his men.
Wood-lined masonry walls, five feet thick, kept powder dry and safe from sparks and flame. But on December 11, 1863, the inner magazine with its store of small arms and munitions mysteriously exploded, killing eleven Confederate soldiers. The leaning brick wall and archway, still visible today, show the force of the blast.