Which of these states do you consider Southern?

[100% pro-life no matter what]

All but Delaware and Maryland.  Though, Missouri is kind of borderline.

[100% pro-life no matter what]

"Appalachia" really deserves it's own distinction from "The South".    The two really do have quite a few differences.

Where is the line between the two, though? Is Tennessee "Southern" or "Appalachian"? Should Pennsylvania be considered part of "Appalachia"?

If you use this distinction, the only state that would purely fit into Appalachia is West Virginia, but parts of Pennsylvania, Virginia, Kentucky, Tennessee, North Carolina, and Georgia would fit as well.  But, by the time you move far enough down the mountain chain to Tennessee (look at places like Knoxville and Chattanooga), the culture is much more Southern than Appalachian.  Plus, over two-thirds of Tennessee lies outside the Appalachian Mountains (even Knoxville isn't really high up at all).  Where I am in Middle Tennessee, it is pretty flat, and parts of West Tennessee have more in common with Mississippi than East Tennessee.

[100% pro-life no matter what]

"Appalachia" really deserves it's own distinction from "The South".    The two really do have quite a few differences.

Where is the line between the two, though? Is Tennessee "Southern" or "Appalachian"? Should Pennsylvania be considered part of "Appalachia"?

If you use this distinction, the only state that would purely fit into Appalachia is West Virginia, but parts of Pennsylvania, Virginia, Kentucky, Tennessee, North Carolina, and Georgia would fit as well.  But, by the time you move far enough down the mountain chain to Tennessee (look at places like Knoxville and Chattanooga), the culture is much more Southern than Appalachian.  Plus, over two-thirds of Tennessee lies outside the Appalachian Mountains (even Knoxville isn't really high up at all).  Where I am in Middle Tennessee, it is pretty flat, and parts of West Tennessee have more in common with Mississippi than East Tennessee.

With this in mind, unless you are getting very specific with your divisions "Appalachia" should just be considered part of "The South", IMO.

I agree and would put West Virginia in the South, even though it's not a perfect fit.  The same applies for Virginia and Florida.

[100% pro-life no matter what]

^ Of course.  Southern Illinois is *The South* in most senses of the word, but the fact is, it's in Illinois, which isn't part of the South.  I know that sounds ridiculous, and if I were making a county map of where "The South" is, I would include parts of several states, but I think if you are doing a map of which WHOLE states fit into the South, you would have to include WV, as most measures include it.

Here was my county level map of the South that I posted in 2013. It splits a number of states in the poll, but only KY and WV have a majority of their population in the South based on this division. MO has a majority of its counties in the region, but not a majority of its population since both KC and St Louis are outside it.

Only east TX is in this split of the South with DFW and San Antonio outside it. Houston is outside, too, but it is on the border and could go either way. Even if metro Houston is added it still would leave most of the state outside.

The last of my reworked states using the Nine Nations of North America are those in Dixie and the Islands. South Florida was part of the Caribbean-based Islands and not in Dixie, and I followed the division from the book. However, in the 30 years since publication one could make the case for central FL to go there, too. Even the Cajun area of south LA could move to the Islands, with a culture unlike most of Dixie as Garreau noted in the book.

Over all there is enough population for 13 states, but the need for some smaller states in other regions drop the number of states in these two nations to 12. Within Dixie the states follow the geography of the Appalachians and Coastal Plain. If there were an additional state it would likely be one that linked Charleston to Jacksonville, leaving central FL and the deep South.

States (and principal city) with 2010 populations in millions are:

Dixie
Chitimacha (New Orleans) 3.7
Caddo (Shreveport) 3.3
Osage (Little Rock) 4.7
Tunica (Memphis) 4.3
Chickasaw (Atlanta) 9.3
Shawnee (Nashville, Louisville) 6.8
Cherokee (Knoxville) 8.8
Powhatan (Virginia Beach) 7.5
Catawba (Charlotte) 7.0
Muskogee (Montgomery, Augusta) 9.1
Seminole (Jacksonville) 9.8

Islands
Colusa (Miami) 7.1

I would include the Dallas, Houston, Oklahoma City, St. Louis, and maybe Kansas City metro areas in the South.

[100% pro-life no matter what]

I would include the Dallas, Houston, Oklahoma City, St. Louis, and maybe Kansas City metro areas in the South.

The first three I could definitely fathom arguments for, but St. Louis and Kansas City?

I get to St Louis fairly often, and it's no more Southern than Indianapolis. Both feel a lot more like Chicago than Atlanta.

There's virtually no way one can consider KC to be anything other than a Great Plains city like Omaha. My family lives in KC and I know it pretty well. From my visits to OKC you could put it in the Plains category or link it with western cities like Denver, but I didn't find it to be Southern at all. I lived and worked in Dallas as recently as the late 1980's and unless it has changed a lot in 30 years I lump it with OKC as either a Plains or Western city, but not in the South.

I'll concede Kansas City, I guess.  But, almost all of the people I know from OKC, DFW, Houston, and STL are very Southern culturally.  I would bet a suburban area in Dallas would have a ton in common with a suburban area of Atlanta or Nashville.