I don't typically divide the South by states, but rather geographic features. Those features greatly influenced how those areas developed.

For Deep South, I'd say it's a combo of two similar, but distinct areas: The southern Atlantic Fall Line to the areas about 50 miles from the coast (at max) and the lower Mississippi watershed. These were the primary spots where cotton grew.

• The Fall Line plains bit goes from where growing transitioned from tobacco in North Carolina and wraps all the way down to the original Black Belt in Alabama and eastern Mississippi. It tends to include the cities directly on the Fall Line, since their development was directly correlated to cotton (Fayetteville NC, Columbia, Augusta, Macon, Columbus GA, Montgomery). There are few larger cities in the rest of the area, though. This lack of major cities often leads to Birmingham and Atlanta being grouped with the region since they are southernmost noncoastal cities near the region and got a lot of migration historically from the area, but they really aren't part of the region. And it's really obvious beyond a just a rural/urban divide. That said, it has a lot of subregions despite the low population, like the Sandhills, the Wiregrass, the Black Belt Prairie, etc.

• The lower Mississippi valley from Arkansas and Tennessee down to just above the coastal areas is the second area (Jackson technically isn't part of the watershed, but it's close enough to include). Overall, think of the Mississippi Delta and the Piney Woods. I'd also include the Louisiana/Arkansas areas of the Red River watershed since it's pretty similar in development. So think Memphis, Jackson, Shreveport, etc. Little Rock acts like a bit of a Fall Line city with the Ozarks, but since the rest of the cities in the region are so flat, it feels weird despite acting more like the cities in the Fall Line plains.

Unfortunately, I do think these two areas will start to split in association. The Lower Mississippi is downstream from a lot of the Midwest and thus potentially more affected by chemicals and industry from that region, and, while the Upland South is growing, as the downstream flow is so split up, it just can accumulate as much when flowing down.

The coastal port areas of the southeast would be lumped in the Deep South as well if you're dividing the south into the two "big" divisions of Deep South (really "Lower South" before the brand change) and the "Upper South." The coastal bits can be divided into three general areas, but they tend to each have a notable subsection.

• The Atlantic coast includes the likes of Savannah, Charleston, Wilmington and Jacksonville. These tend to be among the oldest cities in the south at large. In the north, there's the Tidewater in Virginia and North Carolina around Norfolk which is treated separately from the Gullah region to the south.

• Florida mostly developed way later than the rest of the coast, so it has a different feel. Even then South Florida is different still with its more Caribbean influence.

• The Gulf Coast has a much more mixed European heritage than the Atlantic coast, but grew under similar times. All the cities of Pensacola, Mobile, Biloxi, New Orleans, Baton Rouge, Lafayette, Houston, Corpus Christi all have prominent non-British history and it shows. That said, New Orleans and Lafayette definitely are a notable extreme of this.

As for other regions of the south, they're primarily upland in two disjointed parts: Appalachian and Ozark. That said, Appalachian is big enough with notable development differences to break into parts.

• The southern Appalachian is primarily in west North Carolina, western Virginia, east Kentucky, East Tennessee, North Georgia, Northeast Alabama and a sliver in South Carolina. These are the more coal mining areas of the southeast and a bit of the industrial development of post-Civil War, but terrain limited it a bit. Asheville, Knoxville and Chattanooga are the big cities (Roanoke and Tri-Cities step up in the role when one is needed in those areas), with Greenville and Birmingham being arguable border cities (with Atlanta sprawl, it's northern bits can make a claim too).

• The Piedmont is where the main southern growth has been outside Florida and Texas. There are the eastern foothills of the Appalachians that were generally less desirable for cotton (though it was such a cash cow that it was sometimes grown, but never could get to the scale of the big plantations), but more exploded with industrialization. Atlanta, Charlotte and Greensboro are the pure examples, and despite being a Fall Line city, Raleigh is in this area as well. Birmingham and Greenville are too from the Appalachian side. The western foothills of the Appalachians are pretty similar (except notably less black migration) and hasn't really developed into a known named culture region. So Bowling Green, Nashville, and Huntsville (Birmingham is a border area for this region too. When people say Cincinnati has a bit of southern-ness to it, it more matches this western foothills area.) can be looped in as well despite not being close to Piedmont (Though Lexington and Louisville are a bit too north to wrap in the grouping. I'd say the looping in can only go partially into the Pennyroyal regions at most and doesn't reach the Bluegrass region).

• The Ozarks are a mini Appalachia west of the Mississippi and tends to skip the Piedmont and go straight to the mountains. Little Rock is a border city from the south, but the NWA (Fayetteville) area is the most purely associated metro with the area. After that it drops quite a bit in name recognition, with Branson or Joplin being the biggest names.

Besides that, only really Virginia's lowlands aren't covered (Richmond is the Fall Line city a bit too north to be considered Deep South, but it's not upland either).