The Northwest Ordinance was a law that established the guidelines/requirements for a territory to become a US state. This ordinance was imperative to America's expansion, as this law lead to Ohio, Indiana, Illinois, Michigan, Wisconsin, and Minnesota becoming US states.
Even though this law was passed under the Articles of Confederation, the government takes this concept and implements it into the new US Constitution. This is seen in Article IV Clause 1 of the US Constitution.
