Ohio was the first state admitted from the territory created by the 1787 Northwest Ordinance.
The Northwest Ordinance, enacted on July 13, 1787, organized the Northwest Territory north of the Ohio River and east of the Mississippi River. It established a process by which territories could develop governments and eventually enter the Union as states rather than remaining permanent colonies.
Ohio became the first state formed from the Northwest Territory when it joined the Union on March 1, 1803. The remaining territory later produced Indiana, Illinois, Michigan, and Wisconsin, along with part of Minnesota. The ordinance therefore created an important framework for the early republic's westward expansion.
The law also prohibited slavery in the territory, protected certain civil liberties, encouraged public education, and recognized that Native nations had rights that settlers were not supposed to violate. In practice, enforcement of those provisions was uneven and conflict over Indigenous lands continued for decades.