The Northwest Ordinance was an Act of the US Congress that created the Northwest Territory that was the first organized territory of the United States. It was very important because the Ordinance settled details of the admission process that could be used as a model in other opportunities.
Also, the Ordinance impacted voting rights and office-holding rules, any man that owned 50 acres of property would be entitled to vote and more than that would be needed so that man could be able to serve in government.
Slavery was also forbidden in the Northwest Territory which made the Ohio River become the natural division between free and slave states.