Fort Sumter, a sea fort built on an artificial island at the mouth of Charleston Harbor, was planned after the War of 1812 to strengthen American coastal defenses but remained unfinished because of funding, weather, disease, and technical problems. Named for Thomas Sumter, it became the flashpoint of the secession crisis when Major Robert Anderson moved his U.S. garrison there in December 1860. After failed resupply efforts, Confederate batteries opened fire on April 12, 1861, and Anderson surrendered after 34 hours, in what was widely seen as the Civil War’s opening clash. Heavily bombarded later in the war, the fort remains a major Civil War site.