Northwest Ordinances,also called Ordinances of 1784, 1785, and 1787, several ordinances enacted by the U.S.Congress for the purpose of establishing orderly and equitable procedures for the settlement and political incorporation of the Northwest Territory—i.e., that part of the American frontier lying west of Pennsylvania, north of the Ohio River, east of the Mississippi River, and south of the Great Lakes; this is generally the area known today as the American Midwest.