So, I admit up front that I first thought this was the National Museum of American Art. On the first floor, it seemed exactly that. I went in and turned left and there were no "portraits," per se. It was lots of period art from the 1930's.
As I progressed, most of the art focused on portraiture, but even on the third floor, the art ranged away from portraits into a variety of other art. It wasn't until I sat to write this review that I realized it was the National Portrait Gallery which, for me, is disappointing.
I don't care much for photos of famous dead people, in general. I like a verb in my art, and portraits rarely have them. There are some amazing epic pieces throughout -- paintings of Yosemite and the Rockies, or farmers along the Adirondacks, but portraiture doesn't much appeal to me. It was a nice experience, but I think I liked the architecture more than the building's content. Still, if you love museums, it's worth the stop.
I thought rather highly of the exhibits on space photography, as well as the third floor "storage exhibit," where they show how art is displayed long-term in climate controlled environments.