During colonial times, all of the 13 colonies had slaves at one time or another. However, it does distort things to think of the Middle region and New England region as "slave" regions.
The Southern region used slave labor throughout the colonial times. Slavery was a very big part of the culture and economy. The Southern region was made up of Maryland, Georgia, South Carolina, North Carolina and Virginia.
At the time the colonies were founded slavery was legal in every one of them. It is true that colonies in the South (especially South Carolina) had way more slaves than did the Northern colonies. However, it is not true that any of the Northern colonies had actually banned slavery.
At the time that the Constitution was passed in 1789, five northeastern states had banned slavery, but slavery remained legal in the other eight states.
Vermont was the first state to actually ban slavery, doing so in 1777 before the Revolutionary War had actually ended. Please see the "slavenorth.com" link for the years in which each of the Northern states banned slavery.