Like abolitionists, pro-slavery propagandists used powerful imagery to support their beliefs. In the first half of the nineteenth century, the "sciences" of physiognomy, phrenology, and craniology—the analysis of facial features, shape of the head and skull size—were employed to demonstrate the intellectual and moral superiority of the white race. The scholar Petrus Camper, for example, popularized the theory that the angle of the face was an indication of intelligence – the more vertical the line from the forehead through the nose to the lips, the greater the intelligence. Such pseudo-science provided a rationale for a natural racial hierarchy. In other imagery, Africans were directly compared to lower primates in order to justify their enslavement. Even some abolitionists, who were united against the institution of slavery, believed in scientific racist theories of this sort.

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