Although they didn't have the most glamorous job, Liberty Ships might represent America's contributions to the fighting effort in World War II better than any other craft. Between 1941 and 1945, 2,710 were manufactured at 18 American shipyards, making up the largest class of ships in the history of the world. This massive cargo fleet helped replace the British and American ships decimated by German U-boats, but today, only two remain on the water. One of those—the only that is still in historically accurate condition—is the SS Jeremiah O'Brien, a floating museum moored at Fisherman's Wharf.

With the spirit of its namesake—the first American to capture a British vessel during the Revolutionary War—the O'Brien made 11 voyages during WWII: from England and Northern Ireland to South America, India, and Australia. But just because she's become a history exhibit doesn't mean she doesn't still see some action. On Steaming Weekends (usually the third Saturday and Sunday of the month), while remaining dockside, visitors can see the 2,500-horsepower engine in action, and public cruises scheduled throughout the year prove how shipshape the vessel really is. Any day of the week, guests can explore nearly the entire craft including the flying bridge to the engine room.