The fort was a five-sided structure (although not a regular pentagon but more like the home plate used in baseball). It was a brick structure, 170 to 190 feet long, with walls five feet thick, standing 50 feet over the low tide mark. It was designed to house 650 men and 135 guns in three tiers of gun emplacements, although it was never filled near capacity.
Fort Sumter was built after the War of 1812 as one of a series of fortifications on the southern U.S. coast. Construction began in 1829, using slave labor, and the structure was unfinished in 1860, when the Civil War began.