Question

One of the most important legacies of the Northwest Ordinance was that it prevented the expansion of ________________ north of the Ohio River in the new territories.

Answer 1

It should be-
One of the most important legacies of the Northwest Ordinance was that it prevented the expansion of (slavery) north of the Ohio River in the new territories.
So, the answer is slavery

*Hope this helps

Answer 2

A) slavery

The banning of slavery in the new territories had the effect of establishing the Ohio River as the boundary between free and slave territory in the region between the Appalachian Mountains and the Mississippi River. However, the conflict over slaver would grow until the Civil War broke out in 1861.