Florence Nightingale – widely known as the Lady with the Lamp – is internationally celebrated as the founder of modern nursing. Indeed, Nightingale instituted revolutionary hygienic reforms both during and after the calamitous Crimean War, in which more British troops died from infectious disease than from battle wounds. Far less appreciated is Nightingale’s pivotal role as an innovator in data visualization – a groundbreaking rhetorical system permitting data “to speak for themselves.” How Nightingale evolved from her privileged upbringing as the daughter of a wealthy landed family to a champion of progressive health care reform is an astonishing story – one involving a host of influential collaborators and acquaintances at the highest levels of mathematics and government. Nightingale’s passionate and persuasive powers proved highly successful in contrast to the clumsy efforts of another hygienic reformer, Hungarian physician Ignaz Semmelweis. Nightingale’s success confirms Louis Pasteur’s quotation: “chance favors only the prepared mind.”