a. The secession of Confederate states from the Union.
United States government refused to recognize the rights of southern states. After the election, South was convinced that Abraham Lincoln could end the institution of slavery. South Carolina was the first state which was ceded from Union. With the help of conventions, seven southern states seceded from the Union for the establishment of the Confederacy within three months after the election. This was the most serious session in the history of United States which result in the Civil War where the Union armies defeated Confederacy.
