The United States conducts Shot Priscilla on June 24, 1957. It was the third of 29 nuclear tests conducted at the Nevada Test Site in 1957 as part of Operation Plumbbob. "Priscilla" yielded 37 kilotons. Operation Plumbbob was the longest, most comprehensive test series in the continental United States and became controversial after much of the operation was declassified. Plumbbob released approximately 58,300 kilocuries of radioiodine (I-131) into the atmosphere over a four month period, producing about 32% of all civilian exposure due to continental nuclear tests.