Built on a manmade island in Charleston Harbor after the War of 1812, Fort Sumter became a focal point of tensions between the North and South when Federal troops took up residence in 1861, shortly after the Confederacy was established. Charlestonians took the Federal presence as a threat, and agitation escalated. On April 12 of 1861, the first shots of the Civil War were fired here. Eventually, Confederate troops took the fort. Even if you're not particularly interested in Civil War history, the boat trip from either Patriots Point or City Marina is very pleasant, and often affords the opportunity to see dolphins. The tour takes less than a half-day, all told.