The Ohio River follows the southern limit of the last of the continental glaciers.
Where the Wabash flows into the Ohio River water color contrast on the satellite photos shows the Wabash almost green and the Ohio definitely brown.
The Krugers would have gone downstream on the Ohio, probably close to the right bank, first past historic Old Shawneetown, then Cave-in-Rock.
Wikipedia: "After the Revolution, Old Shawneetown served as an important United States government administrative center for the Northwest Territory. Shawneetown and Washington, D.C share the distinction of being the only towns chartered by the United States government. In early November 1803 Lewis and Clark stopped at Old Shawneetown...." I'm taking the position that the Krugers were the next important explorers to stop there.
Cave-in-rock as a striking 55-foot riverside cave in a cliff by the Ohio which was a stronghold for outlaws.. Although they didn't mention it, I am sure the Krugers would have observed it and knew the story of the "Ancient Colony of Horse-Thieves, Counterfitters and Robbers". You might enjoy reading about it.
Other Illinois towns passed would have been Elizabethtown and the old town of Golconda.
Just upstream of Smithland, Kentucky, where the Cumberland River enters the mighty Ohio from the south, they would have gone through the lock at the Smithland Dam which spans the Ohio. The lock is is adjacent to the Ohio's right bank. This is the first of many large and impressive dams that they would encounter on their way to the Gulf.
The Krugers have faced only two portages since they left Grand Portage on Lake Superior, the carries between the Au Train and Whitefish Rivers to cross the Upper Peninsula, and the Maumee-Wabash portage. Contrast that with Coach Larry Hoff going down the Wisconsin River earlier this year, he had to carry or use his wheels 26 times.
Verlen: "For this time of year, there was a lot of barge traffic on the Ohio River. At Paducah, Kentucky, we had to decide whether to go up the Cumberland or the Tennessee, the backwaters of both are joined together above their dam, about 30 miles upstream, forming two very large lakes. After much questioning we took the Tennessee - which was a good decision. There was very little current along the way."
The confluence of the Ohio and the Tennessee is close to downtown Paducah.
Next: The Tennessee-Tombigbee Waterway