Remember, I am asking about a GERMAN U-boat.
Well, might as well give the answer. It was the UC-97, a WW I German Submarine that actually was never commissioned. It was taken as a war prize and made a grand tour of the East Coast, up the St. Lawrence River and into the Great Lakes.
It got as far South as Chicago. Yes, the CITY of Chicago where she was on exhibit for about 2 years. Then it was turned over to the 9th Naval District who took it out into Lake Michigan and used it for target practice by the USS Wilmette.
The wreckage was found in 1992 about 20 miles east of Highland Park, Illinois and there are plans to raise it, restore it and put it alongside the U-505. The organization that found the ship, Eastland Memorial Society
A&T Recovery, Home page, Navy Aircraft as Artifacts, have already recovered over 30 WW II aircraft that went down in "Michigano" (Algonquin for "Great Lake"). The UC-97 is quite a bit bigger though and does have a number of shell holes to patch up.