Then maps like this come along.
The coloured map shows election results from the South on county level. Blue counties voted for Obama, red ones for McCain (darker hues representing larger majorities). In spite of Obama’s national victory, and barring Virginia, North Carolina and Florida, all Southern states (i.e. all states formerly belonging to the Confederacy) went for McCain.
Fall back to another time and you have this: the black and white map map dates from 1860 (i.e. the eve of the Civil War), and indicates where cotton was produced at that time, each dot representing 2,000 bales of the stuff. The more dots, the more intensive the cotton cultivation at that time.
See the pattern? Even better, here are the two maps overlaid so you can see it better.