Thanks Robert A. Cook, PE.
Coastal defense?
Great Lakes defense?
No! For defense of the carrier against German U-boats.
The German U-boats were sinking hundreds of ships off of the East COast and Gulf coasts of the US during this period. Before that, they were winning the Battle of the Atlantic against Britian in her coastal waters.
SO, since the Germans couldn’t get to Lake Michigan, that was the place to run “practice” aircraft carriers up and down against the wind without needing aircraft, destroyers, mine-sweepers, and other escorts - AND the trained men and weapons and arms and fuel and parts to run all of those extra ships! - who were then released to do their real job protecting real warships and convoys. The practice aircraft were much slower, less highly loaded than the more modern carrier aircraft, so the lower speed of these paddle wheelers was not as important.
Also, since Lake Michigan was “deep water” almost immediately off the pier, they could begin practicing take-offs and landings almost immediately. If you leave Norfolk harbor, you need a long time to get far enough out to sea to do the high-speed runs in rougher water (on average) so you end up wasting even more time.
A simple “day trip” out from Chicago - since they didn’t need to practice night landings, was possible every day at very little expense and without burning extra fuel oil: the paddlerwheelers coal was available right at dockside, and was used by most other merchant ships even. Liberties and Victories and troop ships and military auxiliaries and landing ships and true warships were all oil-burning
Not only did the St. Lawrence Seaway keep the German U-Boats out, the submarines that we built on the Great Lakes couldn’t get to the Atlantic. So, they put them on barges and floated them down the Mississippi.
However, those carriers were very effective in defending our Northern borders. There is no record of any invasion from that direction during World War II.
