When the Colonies exercised their natural right to secede from England, every colony was a slave state. They were *ALL* slave states.
It was actually the words in the Declaration that started the ball rolling towards abolition. The State of Massachusetts explicitly cited the Declaration of Independence in the "Freedom cases" which overturned slavery there.
Pennsylvania explicitly rejected that argument, though.
If what I read is correct, Connecticut didn’t formally outlaw slavery until 1849. Only 12 years before the war commenced.