Baltimore, MarylandMay 1955

On May 7, 1955, at approximately 1820 hours (6:20 p.m.), two metallic objects crashed through the roof of the American Oil Company building at 210 South Russell Street in Baltimore, Maryland. The incident was reported to the Air Force and eventually investigated by Project Blue Book, the USAF's UFO investigation program.

The objects appeared to be made of cast iron or similar metal. One weighed 13 3/4 pounds and the other weighed 9 1/4 pounds. They broke apart upon impact with the roof, and an observer at the scene reported hearing the sound of a receding aircraft immediately after the impact.

The Air Force sent the objects to ATIC (Air Technical Intelligence Center) for analysis. Metallurgists from several companies in Dayton, Ohio examined the pieces. Their findings were consistent and detailed. The objects were confirmed to be cast iron of fairly good quality, with less than one percent silicon in the composition. The experts found evidence of corrosion indicating the metal had been exposed to moisture for some time. Based on their construction and wear patterns, the metallurgists concluded the objects were fragments from an old valve control wheel, the type commonly used on ocean vessels, water and sewerage systems, and steam-regulating assemblies.

One expert proposed that the objects had been "skull-cracked" (broken up in a scrap yard) and launched into the air by that process, striking the building while falling. This theory appeared sound, as there were scrap iron companies operating within a mile radius of the American Oil Company building.

The case was classified as "unidentified" by the Air Force, though investigation records suggest the most probable explanation was that the objects had been released or fell from an aircraft flying over or near Baltimore. The full case file, consisting of 41 pages, is reproduced below as held by the National Archives.