W of Zahl, North DakotaJuly 1958

On the morning of July 30, 1958, a state police officer west of Zahl, North Dakota, reported seeing an unusual object in the sky. The sighting began at 3:30 a.m. local time and lasted about two hours. The object emitted white light with irregular shades of red, blue, and green. It had an undetermined shape with a fuzzy or blurred outline and appeared to be about the size of a pea held at arm's length. The officer watched it travel from the northeast toward the east across the sky.

The investigation that followed included interviews with several witnesses who corroborated key details of the sighting. These witnesses included another state police officer from Tioga, North Dakota, as well as officials in Williston, North Dakota. The U.S. Air Force Technical Information Sheet completed by the primary observer noted that no radar site detected the object, despite checking stations within their coverage range. The sky conditions that morning included scattered clouds, and the observer reported seeing many stars and a dull moonlight.

The Air Force investigation considered whether the object might be an experimental balloon or other device from official U.S. or Canadian sources. However, the report concluded that the reported details made familiar celestial bodies and normal natural phenomena unlikely explanations. An astronomer's analysis and computer calculations revealed that the planet Venus was in the exact location indicated by the observer at the time of the sighting. Given this finding, the Air Force designated the case as unidentified, though the evidence pointed strongly toward Venus as the probable explanation.

The full case file is reproduced below as held by the National Archives, 14 pages.