Are you familiar with John A. Logan and
this book? It's a story I can't believe isn't THE first thing we're taught about the Civil War, but the fact that there's a clear history of the run up to it in Congress, written from someone with first hand knowledge of the speeches of Southern Politicians, and it's buried in favor of all the "Lost Cause" crap speaks VOLUMES to me about this country's intrisic racism. Which of course serves a valuable purpose to divide Americans of the 99% among arbitrary skin color, rather than class (but I digress).
Anyways, he was a Illinois congressman who was initially ambivalent on the question of slavery, but pushed FAR to the
RIGHT on the issue, becoming a fervent abolitionist, and taking up arms himself for the Union. What radicalized him was the outright calls for Yankee blood in congress from Southern politicians, and he wrote the book to document their speeches, word-for-word, for posterity.
There was no ambiguity from their speeches what the war was about...
the book is sadly out of print, but some independent presses are keeping it in circulation. It's not easy to find. Unlike all the "Lost Cause" crap, and pro-southern Civil War histories, which you can find plenty of.