During the American Civil War, Fortifications like Fort Wagner and Little Round Top served as key defensive positions. One particularly significant structure was Fort Sumter in South Carolina. It was the site of the first shots fired in the Civil War on April 12, 1861, marking the conflict's beginning. Other significant defensive positions included the trenches and earthworks utilized during battles such as Gettysburg and Vicksburg. These fortifications demonstrated the strategic importance of geography and constructed defenses in warfare, leading to extensive casualties and pivotal shifts in control throughout the war.