Hmmm...I might be able to help with St. Louis.
--Jefferson National Expansion Memorial (The Old Courthouse and The Arch; The Old Cathedral is on the grounds, but not part of the memorial)
--Union Station
--Forest Park (World's Fair Pavilion, the Zoo, the Art Museum, the Science Center, the History Museum and the Jewel Box)
--University City Loop
--The Sycamore Homestead
There are lots of other places, but I don't know how long you're going to be there. If you want more info, or have any other questions about St. Louis, just ask.