The Confederation Congress established the Northwest Territory, formally known as "Territory Northwest of the River Ohio," on July 13, 1787, as part of the Northwest Ordinance. The area encompassed all American territory west of Pennsylvania and north of the Ohio River, spanning most or large parts of the future states of Ohio, Indiana, Michigan, Illinois, Wisconsin, and Minnesota. In August 1789, Congress under the new U.S. Constitution affirmed the Northwest Ordinance and the Northwest Territory. On July 4, 1800 Congress, in preparation for Ohio statehood, created the Indiana Territory. This legislation placed all of the land west of the Indiana-Ohio border and extending northward in the Indiana Territory, reducing the Northwest Territory to present-day Ohio and the eastern portion of Michigan's Lower Peninsula. When Ohio became a state on March 1, 1803, Congress annexed the remaining land to the Indiana Territory, and the Northwest Territory ceased to exist.
Beverley W. Bond, Jr., "Northwest Territory," Dictionary of American History rev. ed. (New York: Charles Scribner's Sons, 1976), 5:122-23; "An Act to Provide for the Government of the Territory Northwest of the River Ohio," 7 August 1789, Statutes at Large of the United States 1 (1845):50-53; "An Act to Divide the Territory of the United States Northwest of the Ohio River, into Two Separate Governments," 7 May 1800, Statutes at Large of the United States 2 (1845):58-59; "An Act to Enable the People of the Eastern Division of the Territory Northwest of the River Ohio to Form a Constitution and State Government, and for the Admission of Such State into the Union, on an Equal Footing with the Original States, and for Other Purposes," 30 April 1802, Statutes at Large of the United States 2 (1845):173-74.