There was a novel, I'm guessing 1960s or 1970s, about the formation of a black nation in the South. I believe it was five or six present states - South Carolina, Georgia, Alabama, Mississippi and probably Louisiana - but not Florida, that won independence from the U.S. I do not recall whether independence came from negotiations or from military. I do recall that the name of the nation was made up of the initials of the states - so maybe something like GAMSCL (I'm pretty sure that's NOT it).
I do not recall the name of the novel or the author. Anybody else remember this story. I'm guessing it would be of alternate history genre.