Lincoln was a member of the Republican Party, which was opposed to the expansion of slavery into new territories. His election was seen as a threat to the Southern states, which relied heavily on slavery for their economic and social systems.
In response, several Southern states seceded from the Union and formed the Confederate States of America. The Civil War began in 1861 when Confederate forces attacked Fort Sumter in South Carolina. The war lasted for four years and resulted in the defeat of the Confederacy and the abolition of slavery.