One of the three VC-137B's that were at the service of the President of The United States. This one is currently on display at the Pima Air and Space Museum in Arizona. One is at the Nixon Library in Simi Valley and I do not remember where the other one is. I believe it is in the Air and Space Museum part of the Smithsonian. These are the aircraft that brought the Office of President of The United States into the jet age.
The full skinny on the project is at the link below.