To the Indians the main course of the river turned right at what we call the Ohio ~ that's because 90% of the water flow into the lower Mississippi watercourse is provided by the Ohio at that point.
De Soto managed to reach Green River Island at Evansville, and crossed first to that island, created a defense, then crossed to meet the indians at Angel Mounds, then went on over to Vincinnes and Terre Haute and sent a small party north to Lake Michigan to verify the existence of a large lake.
The older analysis that forgot about the name changes had De Soto crossing into Arkansas ~ and one does wonder how he got his horses over there ~ and why he wasn't also caught and eaten by the Cahokia indians much sooner. There's a ford at Leaven's Worth on the Ohio ~ my ancestors crossed the Ohio from the North shore to the South shore at this well known ford. They then settled along the Green River, and claimed Green River Island. No doubt they had a copy of De Soto's travel diary!
I think we can both agree that De Soto covered some serious territory during his exploration of the southern part of the U.S., without getting too distracted by his specific itinerary. De Soto described very large indian populations, particularly around the Mississippi river. The remains of the Mississippian Culture seem to support his testimony. Those large populations were long by the time the next group of Europeans explored the Mississippi.