The quest for roots has been an enduring American preoccupation. Over the centuries, generations have sketched coats of arms, embroidered family trees, established local genealogical societies, and carefully filled in the blanks in their bibles, all in pursuit of self-knowledge and status through kinship ties. This long and varied history of Americans search for identity illuminates the story of America itself, according to Francois Weil, as fixations with social standing, racial purity, and national belonging gave way in the twentieth century to an embrace of diverse ethnicity and...