1. Fort Sumter
This is where the American Civil War started. On April 12, 1861, Confederate forces opened fire on this federal garrison sitting on an artificial island at the mouth of Charleston Harbor, and four years of war followed. Getting here requires a ferry from Liberty Square (about 30 minutes each way), and the $35 ticket covers both the boat and fort entry. The fort itself is smaller than you expect, a squat ruin of brick walls that never got finished to their original height. But standing inside, looking out at the same water the Union soldiers watched, the history hits differently than reading about it. The National Park Service runs the site, and rangers give short talks about the battle and the fort's later use during the war. Construction began in 1829 as part of coastal defenses after the War of 1812, but the fort was still incomplete when the first shots were fired. What remains today is a mix of original brick, wartime damage, and later additions. Allow about 2.5 hours total for the round trip including time on the island. This is the top must-see in Charleston for anyone with even a passing interest in American history. Ferries depart several times daily, with the first boat usually at 9:30 AM and the last return around 4:00 PM. Book ahead online, especially in spring and fall when things to do in Charleston tend to sell out fast. The visitor center at Liberty Square has a small museum worth seeing before you board.