Actually its northern Florida that's considered the South. The Florida panhandle is sometimes called the "redneck corridor". The mason-dixon line definitely does not correctly delineate the border between south and north today; Maryland and Northern Virginia are now considered out of the South. so the South is: northern Florida, Georgia, the Carolinas, southern Virginia, Tennessee, Kentucky, Alabama, Mississippi, Louisiana, Arkansas and eastern Texas.
I wonder where django unchained takes place. If Tarantino sticks to history he'll know that cotton was primarily grown in what is now the "cotton belt", which stretches from Texas on into Arkansas, then through northern parts of the states of Alabama, Mississippi, Georgia and into South Carolina... if you look at a demographic map of the u.s. the same former cotton belt region is today still predominantly african-american.
I know this because i'm a geography buff (was my major in college) and i've lived in northern Florida, Tennessee (primarily), east Texas, Kentucky and South Carolina :D