You should name names.
The historical slave states were New York, New Jersey, New Hampshire, Connecticut, Massachusetts, Pennsylvania, Rhode Island, Maryland, and Delaware.
Also, North and South Carolina, Virginia and Georgia were slave states. Don't ever forget to cast 4/13ths responsibility in that direction for enshrining slavery into the United States Constitution.
Don’t forget mention that slavery was illegal in New York, New Jersey, New Hampshire, Connecticut, Massachusetts, Pennsylvania, and Rhode Island by 1860.