Greetings,
It just so happens that I sailed on the Mississippi River in Iowa for many years.
1. The first plan to maintain a navigable depth was the placement of wing dams that pushed the water to the middle of river. It gave boaters and steamships about a 4.5 foot channel. There are markers on the end of each wing dam (Most of the time). Avoid a short cut over the wing dams. There are all rock.
2: The second plan was the Roller Dams. There hold back the water and give you a least a 9 foot deep channel. Beside each Roller Dam are locks to get from one pool to the next. Off the top of my head there are around 125 locks and Roller dams from St Paul to St Louis. Barge Traffic always takes precedence through the Roller Dams. Some days you can get through quickly... other times you have to wait several hours. Be nice to the Lock Master.
3: There are some incredibly beautiful sights along the River, and in the upper Mississippi there are many islands as well.
https://en.wikipedia.org/wiki/List_of_locks_and_dams_of_the_Upper_Mississippi_River
www.mvr.usace.army.mil/.../Loc...
Now I am on the Great South Bay of New York's Long Island and enjoy salt water sailing.
Rick+