What term was used to describe the rough divide between free and slave states by the mid-1800s. The Mason-Dixon line (between Maryland and Pennsylvania or Delaware)-was used to describe the rough divide between free and slave states by the mid-1800s.
The answer is: Mason-Dixon Line
Mason-Dixon Line marked the northern limit where slavery was still allowed in united states (if you move one stop north from the mason-dixon line, you could be in jail if you owned a slave).
The line has not been moved for around 150 years before eventually the missouri compromise was made and reduce the area where slavery was still allowed.
