Vallée de l'Ohio
After negotiation with the federal government, these states ceded their claims to the United States between 1780 and 1786. In July 1787, most of Ohio Country, the southern peninsula of what is today the state of Michigan, and western Illinois Country were incorporated as the Northwest Territory. In 1803, most of what was formerly Ohio country north and west of the Ohio River was admitted to the union as the state of Ohio.