I want to say it was called The Blue and the Gray but I'm not finding it.
It was a shareware game between maybe 1993 and 1996. \
Game started out either as the north or south and you chose your cabinet. With Lincoln it was possible to get like West Virginia immediately, Kentucky, Tennessee, maybe Missouri. Deep south always seceded but you might get a couple of states to stay if you appoint someone from there in a good position or don't react too aggressively with Ft. Sumter.
Up until Diablo 2 it was probably my most played game. It was a DOS game, had to c: that shit.
Now I'm curious. Are you sure it wasn't north and south?