Maybe I misinterpreted what this is supposed to show. Is this based on data from like 150 years ago or is it based on how things are today?

This is similar to something I saw on reddit over the weekend which was a similar map but based on local cuisine. I live in North Fulton County now, but I'm originally from central Alabama and the dividing line for the cuisine was between "soul food" and whatever other term they had come up for deep fried food

Basically it was white people southern food vs. black people southern food (which, at the end of the day is actually not that different)

curious if this Appalachia vs. "Deep South" thing is really just a racial divide in the data with "Deep South" being African American descendants of slaves across the Black Belt and Appalachia being the more white population

Oh, I saw that map too.

The map in this post is historically based, I think, but they don't say that very loudly.

And definitely some of what we're seeing in this data is a racial divide - but the racial divide in the South goes back to where slave-based agriculture was and was not viable.