Reddit mentions of A Portion of the People: Three Hundred Years of Southern Jewish Life

I honestly don't know how it stacks up percentage-wise in comparison to other cities, but there's definitely a substantial Jewish community in Charleston relative to its small size, and I suspect far higher than in other small Southern cities. Last I heard, there are about 6,000 Jews in Charleston today, and for a city of only about 128k people, that's a far higher percentage than the U.S. in general. There have been Jews in Charleston since the 1600s, believe it or not. Some of the earliest Charlestonian Jews were Sephardic, and later there were a fair number of immigrants from Western European countries, and then most recently, a lot of Jews from eastern/southern Europe ended up there in the early to mid 1900s. I know that my own family members went there simply because they realized they needed to escape from Belarus, and Charleston is where the other people from their town who'd emigrated had gone. As for why that first wave of eastern/southern European immigrants came, I'm not totally sure, but it may have been the fact that there was a long history of other Jews already being in Charleston, so they figured Jews must at least be tolerated there. I do know why the very first Jews came to Charleston: its charter explicitly granted freedom to people of various non-Christian backgrounds, including Jews.

If you happen to be interested in learning more, this amazing book about the history of Jews in the South is probably the best possible resource.