Famous data visualizations I am looking for famous, historical, beautiful, impressive, or otherwise noteworthy visualizations based on statistical concepts. 
I think of examples along the lines of Florence Nightingale's diagram: 

but also "impressive" visualizations of key statistical concepts, such as more special ways to present something like

That is, I think of something like a sister thread to Most famous statisticians or Famous statistical quotations.
Please post one example per answer and provide explanations to (a) support the claim of "famous" or "impressive" and (b) explain why the graphics deserve that reputation.
 A: I'll put up a non-traditional answer: Feynman Diagrams (i.e. not statistical, but definately data related).
Feynman Diagrams are a tool for organizing computations in field theories in physics.  

Feynman first invented them to organize terms in computations in quantum electrodynamics (QED) (so the "data" being organized here are the terms in a very difficult computation).  They are a combinatorial device used to encode all the ways in which certain events can occur in QED, or more formally, all the terms appearing in a mathematical expansion for the probability amplitude of an event.  
They way they organized the data occurring in these computations allowed Feynman to show that QED did not produce infinite probabilities, an achievement called renormalization, for which he won a Nobel prize.  Two other men, Julian Schwinger and Sin-Itiro Tomonaga, also won a Nobel for the same achievement, but it is Feynman's techniques, aided by his diagrams, that have stood the test of time.
A famous example is the Penguin Diagram

which were invented when physicists were discovering that some very natural symmetries did not hold in nature (parity and charge conjugation).
A: Charles Joseph Minrad's https://en.wikipedia.org/wiki/Charles_Joseph_Minard famous map presenting Napoleon's rather catastrophic russian campaign in 1812:

The map shows multiple variables at once, most clear the (diminishing!) number of troops, and where and when they retreated or simply vanished, but also temperature (the below part of the map) and time. 
Edward Tufte https://en.wikipedia.org/wiki/Edward_Tufte said about this map that it

may well be the best statistical graphic ever drawn

see E Tufte: "The Visual Display of Quantitative Information" p. 40. so it certainly belongs in this thread!  
