What term was used to describe the rough ride 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.

warfare was the primary means of cultural transmission in both regions.