Smithsonian Holdings

I know that the Smithsonian has more locomotives than just the ones presently on display, but I never have seen a listing of them. Does anyone have that information?
Second, I knew a guy by the last name of Carter whose family was involved in the lumbering business, Arkansas for one place in particular. His family donated one of their locomotives to the Smithsonian when they ceased operations. I think that it was a 2-6-0. I've seen a painting of the engine, but no photographs. So this is the basis for my curiosity as to what else the Smithsonian may have squirrled away.
And lastly, assuming that I am right, where does the Smithsonian have these locos stored?