Charles Joseph Minard's 1869 flow map of Napoleon's 1812 Russian campaign — the single image Tufte has called the best statistical graphic ever drawn, encoding six variables simultaneously on a single flat surface.
In 1869, the French civil engineer Charles Joseph Minard drew a map of Napoleon's catastrophic 1812 march to Moscow and back. A single image roughly two feet wide, the map encodes six variables simultaneously: the size of the army (represented by the width of a band), the army's geographic position (latitude and longitude), the direction of movement (color: gold for advance, black for retreat), and temperature during the retreat (a scale along the bottom, aligned with the geographic data). Tufte has called it the best statistical graphic ever drawn. Six dimensions of data. Zero chartjunk. Every drop of ink serves the evidence. The map's visual impact is devastating: the gold advance band narrows as hundreds of thousands of soldiers die from disease, exhaustion, and combat; the black retreat band thins to near-invisibility by the time the remnants of the army cross back into friendly territory.
Minard's Napoleon Map
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The map's design demonstrates Tufte's principle of escaping