The XC-99 was located just outside of Kelly AFB when this slide was taken. In 1973 it was owned by the San Antonio chapter of the Disabled American Veterans organization. It was open to the public at that time, with a nominal charge to go up inside it, which we did. At this point there were no longer any USAF markings on the a/c.
This photo was added on 25 April 2021, and has since been viewed 257 times.