Withdrawal from the Federal government of the United States. Southern states, feeling persecuted by the North, seceded by voting to separate from the Union. Southerners felt this was perfectly legal but Unionists saw it as rebellion.
The concept of secession was based on the logic of John C. Calhoun. In his compact theory of government, states retained the essence of their sovereignty when they joined the Union, and they had constitutional authority to leave, or secede from the Union when it served their interests to do so. South Carolina seceded in 1860.
Secession is the act of withdrawing from an organization, union, or political entity. Typically there is a strong issue difference that drives the withdrawal. The word is derived from the Latin term secessio.