A few things off the top of my head for those cities you still have questions about:

Baltimore: The Inner Harbor, of course, but also Fort McHenry and the Edgar Allan Poe House and Museum

New York: One of the all time great (and free!) harbor rides - the Staten Island Ferry, the American Museum of Natural History, the Guggenheim, the Village (The Smithsonian is in Washington)

Cleveland: The Rock and Roll Hall of Fame and Cuyahoga Valley National Park

Baton Rouge: The Old State Capitol

AZBuck