Hell, the Emancipation Proclamation only freed slave in the Confederacy! Maryland was a slave state and in the Union yet they retained their slaves.
For how long? Do they still have slaves there? Was slavery ever abolished in Maryland? If so, how?
And KY, DE and MO.
BTW, Missouri and Maryland freed their slaves by state action before the federal government did. The actual constitutional amendment therefore only freed the (hundred or so in) Delaware and those (a much larger number) in Kentucky.
As did Missouri, Kentucky, and Delaware. Slavery wasn't unconstitutional, so only a Constitutional amendment could end it. If you read the Emancipation Proclamation you would notice that it merely freed the southern slaves, it didn't outlaw slavery. That may seem like a minor difference but what it meant was that southern slaves fleeing the confederacy wouldn't be returned to their owners as the Fugitive Slave Act required. It was also issued by Lincoln in his position as Commander-in-Chief of the Army and Navy and as a war-time measure.