Item
1951 CE.
Shown on the map at 11.669°, 162.242°.
Greenhouse Item was an American nuclear test conducted on May 25, 1951, as part of Operation Greenhouse at the Pacific Proving Ground, specifically on the island of Engebi in the Enewetak Atoll in the Central Pacific Ocean. This test explosion was the first test of a boosted fission weapon, and the second instance of artificial thermonuclear fusion, following the Greenhouse George test on May 9.
Text from the Wikipedia article Greenhouse Item, licensed CC BY-SA 4.0.