1947.06.26
Two days after the famous Kenneth Arnold sighting, in the wake of the event, on 26 June 1947, a medical practitioner, Dr Leon Oetinger of Lexington, Kentucky, together with three other witnesses, saw a large silver globe moving along the edge of the Grand Canyon. It was travelling at high speed and they were quite clear that it was not a balloon or similar object.
(The UFO Encyclopaedia, Spencer)