Northwest Territory

The Territory Northwest of the River Ohio, more commonly known as the Northwest Territory, was an organized incorporated territory of the United States that existed from July 13, 1787, until March 1, 1803, when the southeastern portion of the territory was admitted to the Union as the state of Ohio. Previously, it was part of the Indian Reserve, a territory under British rule set aside in the Royal Proclamation of 1763 for use by American Indians, which was assigned to the United States in the Treaty of Paris (1783).

The Congress of the Confederation enacted the Northwest Ordinance in 1787 to provide for the administration of the territories and set rules for admission as a state. On August 7, 1789, the new U.S. Congress affirmed the Ordinance with slight modifications under the Constitution. The territory included all the land of the United States west of Pennsylvania and northwest of the Ohio River. It covered all of the modern states of Ohio, Indiana, Illinois, Michigan, Wisconsin, and the northeastern part of Minnesota. The area covered more than 260,000 square miles (670,000 km2).