A significant number of Sephardic Jews, tracing their remote origins to Spain and Portugal, immigrated to the United States from Turkey, Greece, and the Balkans from 1880 through the 1920s, joined by a smaller number of Mizrahi Jews arriving from Arab lands. Most Sephardim settled in New York, establishing the leading Judeo-Spanish community outside the Ottoman Empire. With their distinct languages, cultures, and rituals, Sephardim and Arab-speaking Mizrahim were not readily recognized as Jews by their Ashkenazic coreligionists. At the same time, they forged alliances outside Jewish...