The United State conducts the "Harry" test on May 19, 1953. It was the 9th nuclear detonation in the Operation Upshot-Knothole test series at the Nevada Test Site. Shot Harry yielded 32 kilotons, and was the most efficient pure fission device ever detonated with a yield under 100 kt. Due to an unexpected change in the wind, "Harry" caused the highest amount of radioactive fallout of any test in the continental United States, contaminating the city of St. George, Utah. The test was later called "Dirty Harry."