Dear Linda, I didn't study TN but I lived there for a year and as a former teacher I am curious about these things too. I think it is a geographic thing. The TN river runs across the state but does not divid it. The 3 geographic regions are, the mountains, the hilly country, and the flat land that leads to the Mississippi. I know that a lot of the tourist brochures are divided along this way. NC is divided too, the flat ocean shore, the piedmont or rolling foothill, and the Smokey Mtns. Betty