It's not open to the public, but NBC was able to check it out and interview the curator. As an added bonus there is a short video discussing the Oxcart. First the museum video (hopefully embedding this works OK). In the even the embedded video doesn't work, here is the link to the story. The interview is interesting and there is a very awkward silence when Richard Engel asks a question that quite apparently has a classified answer.
And hopefully the embedding works and you can see the video about the A-12. There is a very interesting fact that I learned from this video.