Upshot–Knothole Annie was one of eleven nuclear weapons tests conducted by the United States as part of Operation Upshot–Knothole.

[1] The device used in the blast was a 16 kt Mark 5 Nuclear Bomb - a low yield fission weapon, detonated 90 meters / 300 feet above the ground.

It studied the effect of a 16 kiloton nuclear blast on two wooden frame houses, mannequins, fifty automobiles and eight bomb shelters designed for residential use.

[2] United States troops, television broadcasters, and FCDA officials watched the blast from a trench two miles away.

[2] The homes in the study were constructed in such a way as to minimize the thermal effects of Annie, with an eye towards determining if, in the absence of fire, the basement of the closer home — 3,500 feet (1,100 m) from the hypocenter — might shelter its occupants, while the second — at 7,500 feet (2,300 m) — could remain standing.