The election of Abraham Lincoln as president, without one vote in favor from a southern state, was the key event in a long series of events that ultimately led to war. However, it was not until his inauguration in March of 1861, when he emphasized that war could be averted depending on the actions of the South, that the war actually began.
Tensions had been building within the country for a long time before the Civil War actually began. In fact, conflict from the abolitionists, primarily of the North, and the slave owning states of the South can clearly be seen in the writings of prominent abolition supporters such as Emerson and Thoreau in the decade leading up to the war (Thoreau’s “Slavery in Massachusetts” essay of 1854 is one example).
Several events exacerbated the tensions and ultimately led to war. The Mexican-American war was extremely polarizing with regard to slavery. America’s victory in that war led to the conquest of vast new territories that nearly doubled the size of the country and intensified debates about which states could or could not ban slavery. At the conclusion of the war, the Wilmot Proviso sought to ban slavery in all the territories the U.S. won in the war. The proviso never passed, but it spurred a debate between North-South interests that sparked serious talk of the south’s secession from the nation. John Brown’s raid at Harpers Ferry, Virginia, in October of 1859, which incited an uprising to end slavery, was another element that moved the nation closer to a violent resolution of the North-South conflict.
When Abraham Lincoln was elected with no support from the South in November of 1860, the southern states saw it as a clear sign that they had no voice in national politics and regulations and that their interests were too different from those of the Union.
However, the war did not begin immediately after Lincoln's election, although in the next few months seven states would secede from the Union, and the South would form the Confederate States of America on February 4, 1861.
In Lincoln's inauguration on March 4, 1861, he sent a clear message of his intention to preserve the Union, and the war broke out just a few short weeks later. Lincoln said:
“In your hand, my fellow countrymen, and not in mine, is the momentous issue of civil war. The government will not assail you. You can have no conflict without being yourselves the aggressors. You have no oath in Heaven to destroy the government, while I shall have the most solemn one to preserve, protect, and defend it … We are not enemies, but friends. We must not be enemies. Though passion may have strained, it must not break our bonds of affection. The mystic chords of memory, stretching from every battlefield and patriot grave, to every living heart and hearthstone, all over this broad land, will yet swell the chorus of the Union, when again touched, as surely they will be, by the better angels of our nature.”
The war began on April 12, 1861. Soldiers from the newly-formed Confederates States of America attacked Fort Sumter, South Carolina.