Project Blue Book Case #1344. On June 25, 1952, a bright object was observed over Chicago, Illinois — the third Blue Book unknown from America's second-largest city (joining Cases #1382 from July 3 and #2962 from April 1954). This June sighting came just eight days before the July 3 case, during the wave's rapid buildup.
Chicago's world-class airspace — with Midway as the world's busiest airport and O'Hare under construction — meant any unknown had to distinguish itself from an extraordinary volume of daily traffic. The June 25 sighting's timing, just days before the July wave's explosive outbreak, placed it at the very edge of the acceleration curve.
No conventional explanation was found. The case was classified "Unknown" — establishing Chicago as one of the cities with the most repeat unknowns in the Blue Book files.