[SeeSharp]

Actually there were no slaves in the North. The North were free states.

Maryland, Kentucky, Delaware, and Missouri were officially slave states. Other states also tolerated some degree of slavery. New Jersey for example still had a few (I think four) "indentured servants for life" as late as the 1870 census (which is after the 13th amendment had passed). There was a large open air slave market in Washington itself (which Lincoln had voted against closing when he was a congressman).

[ReverendJames]

"In the context of the American Civil War, the term border states refers to slave states which did not declare their secession from the United States before April 1861. Four slave states never declared a secession:

Delaware, Kentucky, Maryland, and Missouri, and four others did not declare secession until after the 1861 Battle of Fort Sumter:

Arkansas, North Carolina, Tennessee, and Virginia — after which, they were less frequently called "border states". Also included as a border state during the war is West Virginia, which broke away from Confederate Virginia and became a new state in the Union"

Here