In June of 1921, The Tribune announced that the last official shot of the World War had been fired - in Chicago (or in Lake Michigan, at least). A German U-Boat, U.C. 97, had been sunk in Lake Michigan, torpedoed by a US gunboat.
This wasn't exactly a battle - the U.C. 97 had been surrendered to the United States a few years before, shortly after the Armistice. But under the Treaty of Versaille, all trophy ships had to be sunk by July 1st, so the USS Wilmette carried out the duty about 20 miles off of Highland Park. It was said to be the first time a naval gun had fired an explosive shell on the Great Lakes "since Perry whipped the British on Lake Erie in 1813."
The USS Wilmette was the name the Navy had given to the Eastland, which, six years before, had tipped over and killed more than 800 people.
One sailor, Ernie Pyle, later wrote that the ship was "still in sinking condition...it constantly shied to the right and once in a while felt as if it wanted to lie down."
The U.C. 97 is still out there in the water. The wreck was discovered in 1992, but the exact location has never been made public.
More info and pictures from the Eastland Historical Society