This essay examines, in four topics, the events of those decades that gave rise to the notions of endogamous group membership that are still in force today. Terminology Changed shows that the word “Colored,” no longer denoted an intermediate group in the Franco-American culture of the Gulf Coast but became a polite euphemism for any member of the Black endogamous group anywhere. White Children Consigned to Blackness shows that, by far, the strictest enforcement of the one-drop rule in these years was for school segregation, not intermarriage. White Adults Challenged to Defend Their Whiteness offers a slight viewpoint shift to reveal that the one-drop rule did not affect Blacks at all—it targeted only Whites. African-American Complicity shows that far from resisting or challenging the one-drop rule, members of the African-American ethnic community, especially its leadership, embraced it. They enforced it from their side of the color line, as they had in the late antebellum North, as they continue to do today.