H.L. Mencken, no sentimental defender of the oppressed, on "The Anglo-Saxon" (1923):
Civilization is at its lowest mark in the United States precisely in those areas where the Anglo-Saxon still presumes to rule. He runs the whole South--and in the whole South there are not as many first-rate men as in many a single city of the mongrel North. Wherever he is still firmly in the saddle, there we look for such pathological phenomena as Fundamentalism, Prohibition and Ku Kluxery, and there they flourish. It is not in the northern cities, with their mixed population, that the death rate is highest, and politics most corrupt, and religion nearest to voodooism, and every decent human aspiration suspect; it is in the areas that the recent immigrations have not penetrated, where "the purest Anglo-Saxon blood in the world" still flows.
This was no satire. It is historically accurate. A leading cause of the South's cultural, intellectual and economic degeneration were the Iron Curtains of racial purity and ideological filtering that the South slammed down in the antebellum era. It was terrified of the "foreign" and unfamiliar, which carried dangerous potentials, so the South shut itself off from the bustling, chaotic competition of ideas occurring in the North. For roughly a century the South remained culturally backward, socioeconomically impoverished, internally violent, geopolitically isolated, paranoid and ignorant.
Now it's the Republican base.