|Slave Population in the Southern States - Library of Congress|
This beautiful, historic map was a favorite of President Lincoln, who studied it in great detail during the American Civil War. The map is shaded according to the number of slaves living in each county, and Lincoln found that the darker areas also corresponded to high levels of secessionist attitudes. However, as he saw and we now can see, the South was far from monolithic in its number of slaves and attitudes toward secessionism. Click over to the New Yorker to learn more about this map and the history of infographics.