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NARRATOR: By 1860, the United States was so bitterly divided that 10 southern states refused to put Republican candidate Abraham Lincoln's name on the ballot in the presidential election that year. Three of the ten-- South Carolina, Alabama, and Mississippi-- vowed to secede from the Union if he were elected.

ERIC FONER: They did not want to be in a government run by a northern, anti-slavery party.

NARRATOR: Lincoln won by a landslide. Before he was inaugurated, southern governors began forming militias and preparing for battle. They held state conventions to debate and vote on secession.

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On December 20, 1860, South Carolina was the first to formally withdraw from the Union.

ERIC FONER: The Deep South states, that is the real cotton states-- South Carolina, Georgia, Florida, going over to Mississippi, Alabama, Texas, Louisiana-- they seceded one after another after Lincoln's election.

NARRATOR: In February of 1861, those seven states formed the Confederate States of America, but the rest of the South did not follow immediately. States like Virginia and North Carolina waited several more months to decide whether or not to leave the Union.

ERIC FONER: One of the things that we always say as historians is, everything is inevitable after it happens. But, people at the time didn't know what was going to happen. They didn't know a Civil War was on the horizon. Many in the Upper South felt, well, let's just see what happens. The election of a president is not reason to break up the Union.

NARRATOR: But in April 1861, when Union gunboats attempted to resupply Fort Sumter, a federal fort to the now Confederate territory of Charleston Harbor, they were attacked by Confederate artillery. After the Confederate attack on Fort Sumter, the four states of the Upper South-- Virginia, Arkansas, Tennessee, and North Carolina-- were forced to take sides and left the Union for the Confederacy. The bloodiest conflict in American history was now fully joined.