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!)