which established the guidelines by which new states would be added to the united states
Admission to the Union The Admission to the Union Clause of the United States Constitution, oftentimes called the New States Clause, and found at Article IV, Section 3, Clause 1, authorizes the Congress to admit new states into the United States beyond the thirteen already in existence at the time the Constitution went into effect.
Northwest Ordinance The most significant intended purpose of this legislation was its mandate for the creation of new states from the region. It provided that at least three but not more than five states would be established in the territory, and that once such a state achieved a population of 60,000 it would be admitted into representation in the Continental Congress on an equal footing with the original thirteen states. The first state created from the Northwest Territory was Ohio, in 1803, at which time the remainder was renamed Indiana Territory. The other four states were Indiana, Illinois, Michigan, and Wisconsin. A portion (about a third) of what later became the state of Minnesota was also part of the territory.