On November 13, 1963 nuclear weapons were being disassembled for storage at the Medina TX storage site. An accident occurred and almost 56 thousand kilograms of conventional explosives detonated. Three workers present at the site were injured but survived. Igloo 572 was vaporized and a large crater was formed. No nuclear explosion occurred. The marker is at the location of Igloo 572. (Set the time slider at 1/2017 to see the shadow of the crater.)