What event triggered the start of the Civil War?

The attack on Fort Sumter by Confederate forces in April 1861 is recognized as the event that triggered the start of the Civil War. This assault marked the first military engagement of the conflict, as Confederate troops fired on the Union-held fort in Charleston, South Carolina. The assault led President Abraham Lincoln to call for troops to suppress the rebellion, effectively mobilizing the Union states and prompting the secession of additional Southern states.

While the election of Abraham Lincoln was a significant precursor to the tensions that would lead to war, it was the attack on Fort Sumter that ignited the actual armed conflict. The Emancipation Proclamation, issued later in the war, was a strategic move to free enslaved people in Confederate states but did not initiate the war. Similarly, the passage of the Kansas-Nebraska Act heightened sectional tensions by allowing new states to decide on the legality of slavery, but it was ultimately the attack on Fort Sumter that galvanized both sides into open warfare.