The Ohio River played a crucial role for thousands of years, as civilization were built around its proximity. When the Europeans came to the continent, the territory northwest of the river was appropriated by the British to Native Americans as a reservation. Twenty years later, in the 1783 Treaty of Paris, which ended the American War of Independence, this area was given to the United States.
On this day July 13th, in 1787, the Northwest Territory is incorporated by Congress into the U.S. This area covered the current states of Ohio, Michigan, Indiana, Illinois, Wisconsin, and parts of Minnesota for a total of 260,000 square miles.
In the 17th century the Northwest Territory was used by Europeans, for lucrative fur trading. Britain disallowed white settlers anywhere west of the Appalachian Mountains, so when the area was ceded to the U.S., there were over 45,000 Native Americans inhabiting the area. This territory ceased to exist in 1803 when a portion of the territory turned into Ohio.