This essay introduces the first of four societies, within what became the United States, whose color-line customs differed from the mainstream—Barbadian South Carolina. It presents three topics. The Rule of Socioeconomic Class explains that antebellum South Carolina lacked a rule of blood fraction but used a rule of socioeconomic class instead. A Permeable, Shifted Color Line shows that it was acceptable for wealthy White adults to have a Black parent, and that some swarthy White South Carolinians might have been seen as Black elsewhere in the United States. An Echo of Barbados suggests that South Carolina’s unique color line had been adapted from the Barbadian color line.