From colonial times, the power base in SC economically and politically was largely coastal and a short way inland. Most of the population was there in the colonial period and for quite a long time afterward—I don’t think there was widespread settlement in the inland areas until after the Indian removal during Jackson’s presidency.

Unlike other areas in the south, most of SC’s plantation economy (ie the largest farmers who also ended up being on the top of the heap wealth and power wise) was in indigo and rice, grown in the marshy areas along the coast.

It was a terrible environment for the European colonists and attempts at using indentured labor failed miserably as white workers died in huge numbers. However, Black slaves did better—survived more, were sickly less—and so the plantation labor became all slavery based much earlier than states like Virginia.

Just because slaves survived better than white indentured servants didn’t mean that they had a good life by any means. The conditions and the environment in general was more like the brutal sugar plantations in the Carribean than other colonies, and like those plantations, there were a LOT more black slaves than whites. There was an enormous fear of violent rebellion. That was a fear everywhere in the slave states which is why there were so many legal restrictions on slave movement, education, religious practice etc, and free blacks were often legally banned from living in the southern states—all of these were potential routes by which slaves could develop rebellious ideas and/or plan an uprising.

The fear became even stronger after the uprising in Haiti in 1803 ended with the slaves winning and establishing their own country. Then in the 1820s an alleged uprising planned by free black man/former slave Denmark Vesey was uncovered in Charleston. The supposed details of the plan included a huge number of black slaves planning to take part, plans to kill all the white people, and to steal ships and sail off to Haiti. The uprising didn’t happen and while something was probably being planned, rumor and fear blew it into a far larger and more terrifying plot than it likely really was.

The alleged plot scared the crap out of white South Carolinians though. And laws controlling slaves and banning free blacks all together became even stricter and more numerous. Slave patrols were something that went on in most slave areas—groups of men hired to patrol the roads at night on the lookout for escaping slaves or slaves slipping from plantation to plantation to potentially plot another rebellion.

The patrollers and the laws they enforced became the basis for how law enforcement worked and how black people were treated by the law even after slavery ended. Again, this is true in all of the slavery states to different extents, but the character of both slavery and the strictness of controls on slaves were more severe in SC than most Other places so that’s how things remained after the Civil War. A deep seated fear of black violence and an inability to feel safe and comfortable unless blacks were strictly controlled was ingrained into the white cultural milieu of South Carolina and those in power kept the severest laws they could for as long as possible. Even someone like Thurmond, and most other SC politicians until very recently, grew up in that same culture and shared those views.

There were other factors at play in SC too, of course, and everything that I am saying about SC’s fears of rebellion and black violence was true of other slave states but the fear was particularly virulent in SC, maybe because of the feeling of being highly outnumbered, isolated from other white settlements that could help them if there was an uprising, and maybe a feeling that the slaves were justifiably angrier and more potentially violent because slavery conditions were that much harder in SC.