The New York Times looks at a map based on the 1860 census that shows slaves as a percentage of the overall population in a given county. The map, apparently, was key to the US prosecution of the Civil War.
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.
This is part of a larger effort by the Times, called Disunion, to blog about the Civil War.