This term refers to an area of the united states where slavery was not allowed before the civil war.

Free-state, is the right answer.

Explanation:

A free-state in the United States' history was a state where the practice of slavery was prohibited. European conquerors introduced the system of slavery in the Americas.  By the 18th century, it existed throughout all the thirteen colonies of Britain in North America. However, during the Revolutionary War, half of the colonies abolished the system of slavery. The issue of slavery remained a divisive issue throughout the period when the Constitution of the United States was written down. Moreover, it was the major cause of the  American Civil War. However, during this time the United States had 19 free states and 15 slave states.