For any art aficionados visiting Baltimore, I'd also recommend the American Visionary Art Museum, a fantastic experience. https://www.avam.org/
Also in DC, don't forget the Hirshhorn Museum and Sculpture Garden. It's one of my favorite modern art museums in the world, and I live 20 minutes from it. I don't go anywhere near often enough.
One of the best in DC, although it is currently closed.