"Who is Black? One Nation's Definition"
By F. James Davis. To be considered black in the United States not even half of one's ancestry must be African black. But will one-fourth do, or one-eighth, or less? The nation's answer to the question 'Who is black?" has long been that a black is any person with any known African black ancestry. This definition reflects the long experience with slavery and later with Jim Crow segregation. In the South it became known as the "one-drop rule,'' meaning that a single drop of "black blood" makes a person a black.