Slavery Map

Here's an illuminating map dating from 1861 showing the prevalance of slavery in the U.S. The enslaved percentage of the population is shown by county. The variations are striking - counties along the Mississippi could consist of more than 80% slaves, while slavery was quite rare in the Appalachians (remember the people wondering where all the black people were in Cold Mountain?) Edward Tufte would be proud of the map's design; its findings are clear even at a low resolution.
Also note Florida's population of only 140,000, barely bigger than Delaware's, and the smallest of the Confederate states by far. Arkansas was the 10th-largest of the 11 rebel states, and it had more than three times Florida's population. Florida in 1860 was more of a frontier than Missouri was. At the time, Florida's population was concentrated in the northern part of the state; most of the peninsula was barely-habitable swampland. (Hey, it still is!)