Nathan Straus (1848–1931) encompassed worlds. He rose from his Jewish German immigrant family's ruin in Civil War Georgia to become co-owner of Macy's and Abraham & Straus department stores. He helped build American Zionism and cofounded the American Jewish Congress movement. His public service led to a nomination for New York City mayor. This, the first comprehensive biography of Straus, details each of these lives but argues that his most historic achievements lay elsewhere—in philanthropy. Inspired by both his Jewish values and no-nonsense pragmatism, Straus designed, funded, and oversaw four Progressive philanthropic initiatives. The greatest—his demonstration and advocacy campaigns for milk pasteurization—saved the lives of countless thousands of infants in New York City and, ultimately, across much of America and western Europe. Straus also founded America's first TB preventorium for at-risk children: a model for the forty-five more that followed. Partnering with Hadassah, he brought American public health innovations to Mandate Palestine. He provided vast relief for New York City's jobless in the severe 1890s depression. In all, Straus's humanitarianism won the acclaim of American presidents and world leaders and the gratitude of millions. We can learn from him today.