Florence Nightingale used data visualization to communicate public health data and drive policy change in the mid-19th century. She partnered with a statistician to analyze mortality data from the Crimean War, which showed that most soldier deaths were from preventable diseases, not combat wounds. Nightingale created "coxcomb" diagrams to visually depict the data in a clear, compelling way. Her data storytelling had a significant impact, improving sanitary conditions in military hospitals. Today, effective communication of data requires identifying the right audience and tailoring the amount, format and delivery of data to meet their needs.