An obsessive genealogist and descendent of one of the most prominent Jewish families since the American Revolution, Blanche Moses firmly believed her maternal ancestors were Sephardic grandees. Yet she found herself at a dead end when it came to her grandmother's maternal line. Using family heirlooms to unlock the mystery of Moses's ancestors, Once We Were Slaves overturns the reclusive heiress's assumptions about her family history to reveal that her grandmother and great-uncle, Sarah and Isaac Brandon, actually began their lives as poor Christian slaves in Barbados. Tracing the siblings' extraordinary journey throughout the Atlantic World, Leibman examines artifacts they left behind in Barbados, Suriname, London, Philadelphia, and, finally, New York, to show how Sarah and Isaac were able to transform themselves and their lives, becoming free, wealthy, Jewish, and—at times—white. While their affluence made them unusual, their story mirrors that of the largely forgotten population of mixed African and Jewish ancestry that constituted as much as ten percent of the Jewish communities in which the siblings lived, and sheds new light on the fluidity of race—as well as on the role of religion in racial shift—in the first half of the nineteenth century.