deep South definition by Webster's New World
deep South definition by American Heritage Dictionary
deep South - Cultural Definition
The southernmost tier of states in the South: South Carolina, Georgia, Florida, Alabama, Mississippi, and Louisiana. Before the Civil War, these states were centers of cotton production and slavery. All of them seceded from the United States before the firing on Fort Sumter. They are sometimes distinguished from the states of the Upper South (Virginia, North Carolina, Tennessee, and Arkansas), which contained proportionately fewer slaves prior to the Civil War and which seceded only after the firing on Fort Sumter.