Whether you're obsessed with the presidents, literary figures, historic rich Americans--anything from the famous to the infamous--then there's surely a gem here for you. This free museum is part of the Smithsonian Institution. It shares a building with the Smithsonian American Art Museum (which is also free and easy to end up in from the former).
The museum is large, but manageable, meaning you can walk through most of it in just a few short hours. While it hosts the kinds of staple items you'd imagine, like portraits of all of the American presidents, there are also spaces for rotating exhibits which include new media, contemporary photography and painting, and other interpretations.
Do not miss the ever-stunning Kogod Courtyard for a break between museums, or a quick cafe snack and beverage.