Upshot-Knothole Harry was a nuclear weapons test conducted by the United States as part of Operation Upshot-Knothole

Operation Upshot-Knothole

Operation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site.Over twenty-one thousand soldiers took part in the ground exercise Desert Rock V in conjunction with the Grable shot...

. It took place on May 19, 1953 in Yucca Flat

Yucca Flat

Yucca Flat is a closed desert drainage basin, one of four major nuclear test regions within the Nevada Test Site , and is divided into nine test sections: Areas 1 through 4 and 6 through 10. Yucca Flat is located at the eastern edge of NTS, about ten miles north of Frenchman Flat, and from Las...

, in the Nevada Test Site.

The test device, codenamed Hamlet, was detonated atop a 300 foot tower.

The Harry test released an unusually large amount of fallout (the highest of any test in the continental U.S.), much of which later accumulated in the vicinity of St. George, Utah

St. George, Utah

St. George is a city located in the southwestern part of the U.S. state of Utah, and the county seat of Washington County, Utah. It is the principal city of and is included in the St. George, Utah, Metropolitan Statistical Area. The city is 119 miles northeast of Las Vegas, Nevada, and 303 miles ...

. Because of this, the shot would become known as "Dirty Harry" in the press when details were released publicly. It would be among the most controversial of the U.S. nuclear weapon tests.