I found this video this morning. It explains why & how all the history of the flood controls of the entire Mississippi Valley came into being. In 1927 was a massive flood killing hundreds. The Big 4 Lakes are part of this project. The History is very worth watching.
This video provides Understanding of why the system was built not just the Knowledge of it's existence.
https://www.youtube.com/watch?v=cphOrfWcjkE

