Fort Sumter represents sectionalism because it was the site of the first battle of the American Civil War, which was fought primarily because of the growing divide between the North and the South over issues such as slavery and states' rights. The fort was located in Charleston Harbor, South Carolina, which was a hotbed of secessionist sentiment leading up to the war.
The Confederacy saw the Union's continued presence at Fort Sumter as a symbol of Northern aggression and an infringement on their sovereignty. The Union, meanwhile, saw the fort as a symbol of their authority and the need to maintain the Union.
The conflict over Fort Sumter exemplifies the deep-seated sectionalism that existed in the country at the time, with both sides unwilling to compromise on their beliefs and values. The battle at Fort Sumter marked the beginning of a long and bloody civil war that ultimately resulted in the preservation of the Union but also had far-reaching social and political consequences for the nation as a whole.