Maryland, Kentucky, Missouri and Delaware were Union states. They didn't need to negotiate to preserve slavery, the Union merely recognized that these states had that right.
Look, you can keep talking "Slavery, slavery, slavery, slavery, slavery, slavery... but you aren't going to change the truth of the matter that the Union kept slavery for "Four Score and Seven Years", plus another eight months after it was abolished in the South.
We know why you push the slavery dodge, because without it you don't have a good reason to invade other people's land and murder 750,000 men doing it.
The bloodshed on the hands of the Union government demands an explanation, so one has been provided by the Union government. It is the false claim of a war for freedom, when in fact it was the very opposite of that.
It was a war to establish a larger slavery by making the states Vassals of Washington and it's powerful wealthy allies in the North East.
Same problem we face today.
My #96 was simply a response to your attribution of “bad,” to the seceding States. I realize that there is much wisdom in your other posts.