After the 1860 presidential election, eleven southern states seceded from the United States, and many White southerners believed the new administration threatened slavery, the cornerstone of their society. The seceded states formed the Confederate States of America, and the nation entered a civil war. From 1862 to 1864, Confederates built Fort Fisher, a massive earthwork fortification of sand and timber, often forcing African Americans and American Indians to do most of the construction. Its walls stretched from ocean to river on the land face and more than a mile down the beach on the sea face, and the fort grew to include towering walls, underground tunnels, bombproof shelters, ammunition magazines, and 44 large seacoast cannons. Fort Fisher guarded Wilmington, a port city with railroad access to Richmond, while Confederate soldiers there protected blockade-running ships against the U.S. naval blockade offshore. The U.S. Army and Navy attacked Fort Fisher in December 1864 and January 1865, and on January 15, 1865, U.S. forces captured it. A combined 3,837 men were killed, wounded, captured, or missing in the fighting. The fall of Fort Fisher effectively closed Wilmington, then the Confederacy's only remaining supply route for vital foreign weapons, and the Civil War ended about three months later. Only about 10 percent of the fort remains today, as much of it eroded into the ocean, some surviving sections were altered during World War II for military training and airstrip construction, and part of the land face was rebuilt in 2024.