Shot Eddy was the first nuclear detonation of Operation Hardtack II, fired on 19 September 1958 from a balloon at 152 metres above Area 7b of Yucca Flat, Nevada Test Site. It was a successful Los Alamos Scientific Laboratory weapons development test, producing 0.083 kilotons within its predicted range of 0.075–0.15 kt. Operation Hardtack II was the continental phase of Operation Hardtack, conducted entirely at the Nevada Test Site between 12 September and 31 October 1958. The series comprised 37 tests — 19 weapons tests and 18 safety experiments — the largest test series conducted up to that point. It was driven by an imminent hard deadline: negotiations for a nuclear test moratorium were set to begin at midnight on 31 October 1958, and both weapons laboratories rushed as many device types as possible to the test range. The total yield of the entire series was just 45.8 kilotons — a fraction of the 74 kilotons of the single Hood shot in the preceding Plumbbob series — reflecting both the low-yield focus of the tests and growing concern about domestic fallout. LASL shots in Hardtack II were named for New Mexico counties; Eddy County takes its name from Charles B. Eddy, a railroad promoter instrumental in the development of southeastern New Mexico.