Lake Pepin, Wisc., February 1958February 1958

On the night of February 22, 1958, observers in Minnesota and Wisconsin reported seeing a bright, falling object streaking across the sky. One witness claimed the object impacted Lake Pepin, Wisconsin, creating a steam or vapor cloud.

The main witness at Lake Pepin was described as a 65-year-old member of an astronomy club. A second observer near Minneapolis reported seeing a bright ball falling at about a 15-degree angle from vertical. Other witnesses from the Minneapolis area, including someone watching television, also described seeing a large fireball with colors ranging from white to red to green, falling straight down with a long tail. The sighting lasted roughly three to nine seconds.

The object was said to have made a sound like an explosion upon impact. Initial descriptions compared its size to a plate or even a rocking chair, depending on the observer. The Air Force investigators noted that multiple witness accounts suggested the object fell southwest of Minneapolis, though the Lake Pepin witness was the only one claiming to have seen the actual impact.

Air Force investigators traveled to the area in early March to follow up. They found that the game warden for Lake Pepin reported discovering 39 unexplained holes in the lake ice around February 25, though the warden could find no object or hole directly caused by an impact. The investigators concluded that weather conditions on the night in question were clear, and that the object could have been a meteorite or possibly something man-made. However, Lake Pepin was frozen and covered with snow, making any recovery operation impractical. Because no physical evidence could be recovered or confirmed, the investigators recommended no further action, though they noted the sighting appeared to be of a genuine object of either known or unknown origin.

The Air Force ultimately classified the incident as unknown. The case file is reproduced below as held by the National Archives, consisting of 24 pages.