The "Yankee" shot, 14 May 1954 (GMT), during the Castle series of nuclear weapons tests in the South Pacific. While its predicted yield was 9.5 megaton, the actual yield was 13.5 megatons, making it the second largest nuclear test in U.S. history. According to the caption on the back of the photo, "this photo was taken at a height of approximately 12,000 feet--50 miles from the detonation site. Two minutes after Zero Hour, the cloud rose to 40,000 feet--the height of 32 Empire State Buildings. Ten minutes late, as it neared its maximum the cloud stem had pushed upward about 25 miles, deep into the stratosphere. The mushroom portion went up to 10 miles, and spread for 100 miles." (For details on the Castle test series, see information collected by High Energy Weapons Archive, at <htttp://>)

[Source: National Archives, Still Pictures Division, Air Force Collection 342-B, box 911, file 04-0588]