I'm of the impression that proper southern cornbread is the version without sugar (as well as cooked in a preheated cast iron skillet that goes back into the oven), whereas northern cornbread has sugar. (Wikipedia mostly agrees, at least on the sugar front).

This caused me problems when I tried to make cornbread on my own for the first time after moving north for college. It wasn't as good as I remembered from home until I realized I had to take out the sugar.