Answer: The problem caused by the Northwest Ordinance of 1787 was that it limited the future growth of slavery into the western territories. While stopping the spread of slavery was a positive thing, this prohibition led to tensions between slave states and free states.
Step-by-step explanation:
The Northwest Ordinance chartered a government for the Northwest Territory, provided a method for admitting new states to the Union from the territory, and listed a bill of rights guaranteed in the territory.