Same for the National Gallery of Art (i.e. open Easter). Holocaust Memorial Museum closes only 2 days a year - Christmas and Yom Kippur.

It would be very unusual for any of the paid-admission museums (Corcoran, Phillips, Newseum, Spy Museum, etc.) to be closed on what would be a high-demand holiday.

The new US Capitol Visitors Center (well worth a visit) is never open on Sunday. It is also closed on Thanksgiving Day, Christmas Day, New Year’s Day, and Inauguration Day.