Did you know that inconceivably large salt mines exist underneath Lake Michigan and Lake Huron containing trillions of tons of salt?
Neither did I.
Learn about that and more: “The Creation of the Great Lakes”
Related, from 2008 on my old Wordpress site: “From the Shores of Ancient Lake Chicago”. Did you know there are multiple Continental Divides in the U.S., and one of them runs through the Chicago area, delineating the boundary between runoff that ends up in the Great Lakes and runoff that ends up in the Mississippi River? It runs right through Oak Park, Illinois, where I lived in for over 10 years — never once did I hear about that while living there.