I seem to remember, when I was in graduate school, one of my professors, himself a native North Carolinian, mentioning a book entitled South of the James Lies Dixie, meaning south of the James River in Virginia.
good point, I have heard this before about the James River divide. Most texts on regionalism in the US will list the criteria on how the regions are defined. And there are really not exact boundaries of the Dixie cultural region. Many geographers would prefer not putting either Appalachia or the Ozarks inside the Dixie region, but would give them their own separate regional identities.
When I travel, I know that I am back in Dixie when in the small towns I travel thru I see more than one Southern Baptist church and a Dairy Queen all on the mainstreet of the town!