Stolen from wikipedia: Storax Sedan was a shallow underground nuclear test conducted in Area 10 of Yucca Flat at the Nevada Test Site on 6 July 1962 as part of Operation Plowshare, a program to investigate the use of nuclear weapons for mining, cratering, and other civilian purposes.[1] The radioactive fallout from the test contaminated more US residents than any other nuclear test, and the Sedan Crater is the largest man-made crater in the United States, and is listed on the National Register of Historic Places
