I'll disagree with you Annfan, Lincoln violated the very spirit of the Consitution, as well as the letter of it. Your history isn't correct, slavery was one issue among many, and it was the club used by the north to justify invasion of a sovereign State.
Slavery dear was LEGAL at the time, morally reprehensible yes (just like abortion today), but it was legal. The industrial north had colonized the southern States economy with tariffs and price controls. The addition of none slave holding States was another issue, which was a political tool to further isolate the south and marginalize them in Washington. No defense of slavery but it wasn't the only reason for secession.