Over several weeks in March and April 1966, large numbers of people around Dexter and near Hillsdale College in Michigan reported glowing lights hovering and moving low over fields and marshland. The reports included police officers and scores of students. The US Air Force sent its scientific consultant, astronomer J. Allen Hynek, to investigate, and at a heavily attended press conference he suggested that at least some sightings might be marsh or "swamp gas" igniting over the wetlands.
What is on the record
The wave is well documented through the volume of witnesses and the official response, which is what anchors it. Hynek's swamp-gas remark was offered as one tentative explanation for a single faint light, not for the major sightings, but the press stretched it to cover the whole wave, and it was seized on and widely ridiculed. The uproar fed the Congressional hearings that Congressman Gerald Ford called for soon after. The underlying sightings were never uniformly explained. One document sits in the file, a CIA record entered as investigator reporting rather than a primary government file, so no primary paperwork corroborates the wave itself.
Why it sits where it does
The Michigan wave grades L3 in this archive, independent witnesses, carried by the sheer number of separate claimants rather than by paperwork: twenty-six claimants across fourteen videos and three channels describe the same weeks of sightings. The grade reflects the breadth of testimony, not a conclusion about the lights. What the record holds is that many people, including police, reported low lights over the same areas on the same nights, and that the Air Force's own handling of the story became the part best remembered. What was over the fields is not resolved here.