The post-American Revolutionary War Territory Northwest of the River Ohio, more commonly known as the Northwest Territory encompassing most of the pre-war territory of the Ohio Country, was an organized incorporated territory of the United States spanning most or large parts of six eventual U.S. States. It existed legally 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, and the remainder was reorganized by additional legislative actions.