USS Cobia can be found at the Wisconsin Maritime Museum in Manitowoc, about an hour north of Milwaukee. The Maritime Museum honors Great Lakes seafaring, and particularly the shipbuilding industry in Manitowoc. In all, 28 submarines were built in Manitowoc during World War II.
Museums - History, Sea - Military - Submarines
The Cobia is in excellent condition, and due to the Museum's guided-tours-only policy, has suffered no visible vandalism over the years. The closed hatches also means you get a very strong, enjoyable whiff of diesel touring the boat. The forward escape hatch is open into the torpedo room, and there are mirrors in the conning tower allowing a view of the space and equipment. The tour includes a test of the diving alarm, and the guides are knowledgeable and friendly.
The Museum has a good collection of maritime exhibits and artifacts, including submarine-specific memorabilia and a fine collection of civilian and Coast Guard ship models. Easy to find - there is a large Budweiser brewery across the river (how could they allow one of those in Wisconsin?) and open year-round, the Cobia and Maritime Museum are a must-see when traveling in eastern Wisconsin.