War Mortality Diagram by Nightingale

Florence Nightingale is described as "a true pioneer in the graphical representation of statistics".

She is credited with developing a form of the pie chart now known as the polar area diagram, or occasionally the Nightingale rose diagram, equivalent to a modern circular histogram, to illustrate seasonal sources of patient mortality in the military field hospital she managed.

In the year 1855, during the  Crimean War, Nightingale was in the war scene serving as a manager of nurses. She made use of the diagram to tell her story with data by showing the staggering amount of deaths due to preventable disease (shown in blue/grey).  After this
visualization , sanitation became a major priority for the British Army.

Sources:

https://en.wikipedia.org/wiki/Florence_Nightingale