Because of Lincoln's stand on slavery , not the total abolishing of slavery but to keep it in the South only and thus strangling out the institution and his siding with the Republican party and being their standard bearer in the election of 1860, it was a foregone conclusion that the South would eventually secede from the Union . They did so beginning with South Carolina in late 1860 and the formation of the Confederate states of America in early February 1861. When Lincoln was eventually inaugurated in March 1861, and the refusal to abandon Fort Sumter in April 1861 then the war began with its bombardment on April 12, 1861.