The Northwest Ordinance established a process for admitting new states in 1787.
The Confederation Congress adopted the ordinance on July 13, 1787, shortly before the Constitutional Convention completed its work in Philadelphia. It organized the Northwest Territory, the land north of the Ohio River and east of the Mississippi River that the United States had acquired after the Revolutionary War.
The law described a territorial government and a path from territory to statehood. Once a territory reached a population threshold, it could form a constitution and seek admission on an equal footing with the existing states. Ohio, Indiana, Illinois, Michigan, and Wisconsin were later formed from the territory.
The ordinance also prohibited slavery in the Northwest Territory, although it did not end slavery elsewhere and included provisions affecting fugitives. Its approach to territorial expansion became an important model for later U.S. land laws. The ordinance remained significant even after the Constitution replaced the Articles of Confederation.