The fort in South Carolina bombarded by Confederate forces starting the Civil War on April 12, 1861, was Fort Sumter.
Fort Sumter stood on a man-made island guarding the entrance to Charleston Harbor. Although South Carolina had seceded, the fort remained under United States control, making it a major flashpoint between the federal government and Confederate authorities.
At 4:30 a.m. on April 12, Confederate batteries opened fire after the Union garrison, commanded by Major Robert Anderson, refused demands to surrender. The bombardment lasted about 34 hours. Anderson surrendered on April 13 and evacuated the fort the next day. No soldiers were killed directly during the battle, though two Union men died during the surrender ceremony when a cannon accidentally exploded.
Fort Sumter is often confused with Fort Moultrie, Fort Johnson, and other Confederate firing positions around Charleston Harbor. Those sites fired on Sumter; Sumter itself was the fort under attack. The battle is conventionally treated as the opening engagement of the American Civil War.