In a country of immigrants, white supremacy has been a curious and lasting preoccupation. Not just African Americans, but Catholics, Eastern Europeans, Italians, Jews, and all races not of Western European origin have been singled out as inferior at one time or another in United States history. But where did such behavior come from, and why do so many continue to cling to such a backward creed? The simplest answer is that racism and racist organizations provide a comprehensive world view in times of social turmoil, a way to interpret changes in social mores and often mystifying economic setbacks. But this is not enough. In virtually every country, bigotry exists, but in ostensibly classless, egalitarian America, it remains one of the most paradoxical features of our social landscape.

Until recently, white supremacy was very much the norm. At the turn of the twentieth century, most labor...