Why was the northwest ordinance of 1787 enacted

It established the precedent by which the United States would expand westward across North America by the admission of new states, rather than by the expansion of existing states. The banning of slavery in the territory 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.

The NW Ordinance of 1787 allowed the US government to split up and sell the land in the area of the Ohio Territory.