Which event is considered the catalyst for the start of the Civil War?

The attack on Fort Sumter is widely regarded as the catalyst for the start of the Civil War because it was the first military confrontation between the Union and the Confederate States. On April 12, 1861, Confederate forces opened fire on Fort Sumter, located in South Carolina, which was a Union fort. This attack marked the transition from a period of escalating tension and political conflict over issues such as slavery and state rights to actual armed conflict.

The significance of Fort Sumter lies in its role as a clear signal that negotiations and compromises had failed, and both sides had chosen to resolve their differences through military action. The attack rallied the North, leading to President Lincoln's call for troops to suppress the rebellion, and it solidified the divide between the Northern and Southern states.

While the Dred Scott Decision, the Kansas-Nebraska Act, and the election of Abraham Lincoln were all critical events that heightened tensions and contributed to the atmosphere leading to the war, they did not provoke immediate armed conflict in the way that the assault on Fort Sumter did.