The Smithsonian Air and Space Museum out at Dulles airport (40 miles outside DC) is also excellent. Far better than what I remember to be at the location in downtown DC.
At the Dulles location they have the Enola Gay and a number of WWI and WWII planes of significant historical value. Definitely worth the trip. It is free but parking will cost you $15 a car.
Again though, if I could only go to one, I’d choose Wright-Pat.