DC Mayor Muriel Bowser has announced the lifting of city-imposed mandates that require proof of vaccinations (as of Feb 15) and the wearing of masks in many public areas starting March 1. The Smithsonian will continue to require face coverings by all visitors ages 2 and older while visiting its museums and indoor spaces until further notice. (FYI - most Smithsonian food service is still closed.)
Other locations can decide to require masks as well so be aware of signage as things continue to change rather quickly.