If that's Maryland, it had slaves. New Jersey was also a slave state. Both remained in the Union, as did of course, Maryland. Delaware was a special case, with few slaves. Lincoln had a plan to buy their slaves into freedom, and use them to colonize part of Nicaragua just to show it could be done. Got turned down.
Further South, Kentucky and Missouri remained in the Union, but held onto their slaves, past the Emancipation Proclamation, which only applied to slaves in the Confederacy.
While this is all interesting history, all of the slave-holding Union States had emancipation plans, held in abeyance until after the war.
It should be noted that MD, MO, WV and various other states excluded from the Emancipation Proclamation freed their slaves by state action befoe the end of the War. The 13th Amendment freed slaves only in DE (a couple hundred) and KY (around 50k).
While this is all interesting history, all of the slave-holding Union States had emancipation plans, held in abeyance until after the war.
If you are going to make such an astonishing assertion, you need to be able to prove it.
For it to be true, one would have to assume southerners were all really, really stupid.
Any intelligent person of the time knew that the South's best hope for independence was foreign, particularly British, recognition. British public opinion was unaminously anti-slavery. As long as the War was between a pro-slave Union and a pro-slave CSA, British recognition was conceivable. Which was precisely why Lincoln issued the Emancipation Proclamation. At a single stroke, it ended the possibility of UK recognition.
Intelligent southerners knew that passing laws for emancipation, even very gradual emancipation, would immediately revive the chance for foreign assistance. Yet it was never seriously considered.
IOW, given the choice between slavery and independence, the South could not choose, since the reason they insisted on independence was to protect slavery.
I'll await your evidence of state plans to abolish slavery after the war. I suspect I'll be waiting a very long time.
Mayland was a separate nation in the Appalachians. Mayland seceded from the Confederacy immediately after the southern states seceded from the Union.