Stuff to do in Washington DC...
National Geographic Museum Store
https://www.nationalgeographic.org/society/events-and-experiences/
DEA Museum
National Law Enforcement Museum
National Postal Museum
National Inventors Hall of Fame and Museum
Union Station
Zero Milestone
Dupont Underground
(if the art’s not too scary): www.dupontunderground.org
National Archives
Library of Congress
National Museum of Natural History
Bit further afield...
Air and Space Museum
Baltimore and Ohio Railroad Museum
Harper’s Ferry
https://www.lonelyplanet.com/usa/west-virginia/harpers-ferry