Green River Lakes Area, Wyo, October 1958October 1958

On October 9, 1958, at 7:40 p.m. Mountain Standard Time, three men were stuck in a pickup truck on a remote road near the Green River Lakes area in northwestern Wyoming when they spotted a glowing object in the sky. The men were moose hunting and happened to be facing south-southeast when one of them noticed the bright bluish-green light low on the horizon, about 20 degrees above it. They watched the object for 15 to 17 minutes using binoculars, then with their naked eyes.

The object stayed in roughly the same area but moved in sharp, jerky patterns. Its brightness changed from moment to moment, sometimes becoming dimmer, then bright again, much like the tumbling motion the observers had seen in the satellite Sputnik. The men said the object remained the brightest thing in the sky until it gradually faded and disappeared. Occasionally they thought they saw a second object to the left, but they believed this was an optical after-image from their eyes.

The Air Force later sent officers to interview the observers in May 1959. The men confirmed their detailed account and noted important differences from Sputnik: the UFO was greenish in color rather than yellowish-orange, it was much brighter, and its flight path was far more erratic and irregular. They also emphasized that the sky had been completely clear that night with no clouds and unlimited visibility. Weather analysis from the National Weather Records Center confirmed that a temperature inversion existed in the area that evening at high altitude, a detail the Air Force examined during its investigation.

The case file notes that the star Fomalhaut was low on the horizon near where the sighting occurred, and suggests that mountain terrain and atmospheric refraction effects may have been involved, though a final conclusion does not appear clearly stated in the file. The complete case file of 23 pages is reproduced below as held by the National Archives.