Let's not forget that every single "Union" state had abolished slavery long before the Civil War, save one.*
It's hilarious when they refuse to call Missouri, Kentucky, and Maryland "Union" states when they fought for the Union. It's almost like they don't want to admit those union states had slavery until the 13th.
"The emancipation proclamation freed the slaves" they say. They don't even provide an asterisk to point out that it only applied to the confederacy and not their own slave holding states within the Union because they are "border" states.