Project Blue Book Case #3565. On May 23, 1955, a bright object was observed over Cheyenne, Wyoming — home to F.E. Warren Air Force Base, which would become one of the most important ICBM installations in the country. While Warren was primarily a support base in 1955, it would soon host Atlas and then Minuteman intercontinental ballistic missiles, its missile field eventually spanning across Wyoming, Nebraska, and Colorado.
Cheyenne sits at over 6,000 feet on the high plains at the edge of the Laramie Range. The city's elevation and clear, dry atmosphere provided excellent visibility. F.E. Warren's growing missile mission made the area's airspace increasingly sensitive.
The case was classified "Unknown."