"Sold for the Benefit of the Sick and Wounded Soldiers"

"The map reaffirmed the belief of many in the Union that secession was driven not by a notion of 'state rights,' but by the defense of a labor system. A table at the lower edge of the map measured each state’s slave population, and contemporaries would have immediately noticed that this corresponded closely to the order of secession. South Carolina, which led the rebellion, was one of two states which enslaved a majority of its population, a fact starkly represented on the map."

Susan Schulten in The New York Times discusses "the United States Coast Survey’s map of the slaveholding states" from 1861, one of the first-ever maps to use shading to depict demographic information.