The most significant fact about American slavery, one it did not share with other prominent ancient slave systems, was its basis in race. Slavery in the United States created a defined, recognizable group of people and placed them outside society. And unlike the indentured servitude of European immigrants to North America, slavery was an inherited condition.
As a result, American slavery was tied inexorably to white dominance. Even people of African descent who were freed for one reason or another suffered under the weight of the white supremacy that racially based slavery entrenched in American society. In the few places where free blacks had some form of state citizenship, their rights were circumscribed in ways that emphasized their inferior status—to them and to all observers. State laws in both the so-called Free States and the slave states served as blueprints for a system of white supremacy. Just as blackness was associated with inferiority and a lack of freedom—in some jurisdictions, black skin created the legal presumption of an enslaved status—whiteness was associated with superiority and freedom.
The historian Edmund Morgan explained what this meant for the development of American attitudes about slavery, freedom, and race—indeed, for American culture overall. Morgan argued that racially based slavery, rather than being a contradiction in a country that prided itself on freedom, made the freedom of white people possible. The system that put black people at the bottom of the social heap tamped down class divisions among whites. Without a large group of people who would always rank below the level of even the poorest, most disaffected white person, white unity could not have persisted. Grappling with the legacy of slavery, therefore, requires grappling with the white supremacy that preceded the founding of the United States and persisted after the end of legalized slavery.
Consider, by contrast, what might have happened had there been Irish chattel slavery in North America. The Irish suffered pervasive discrimination and were subjected to crude and cruel stereotypes about their alleged inferiority, but they were never kept as slaves. Had they been enslaved and then freed, there is every reason to believe that they would have had an easier time assimilating into American culture than have African Americans. Their enslavement would be a major historical fact, but it would likely not have created a legacy so firmly tying the past to the present as did African chattel slavery. Indeed, the descendants of white indentured servants blended into society and today suffer no stigma because of their ancestors’ social condition.
That is because the ability to append enslaved status to a set of generally identifiable physical characteristics—skin color, hair, facial features—made it easy to tell who was eligible for slavery and to maintain a system of social control over the enslaved.