Statistics for occurrence #1 of “Ohio river” in chapter 2.6 of Southern Historical Society Papers, Volume 1.:

...Virginia, North Carolina, South Carolina and Georgia--thirteen in all. At that time all the country west of the Alleghany mountains was a wilderness. All that part of it which lies north of the Ohio river and east of the Mississippi, called the Northwest Territory, and out of which the States of Ohio, Indiana, Illinois, Michigan, Wisconsin and a part of Minnesota have since been carved, belonged to Vi...
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