Operation Plumbbob
1957 CE.
Shown on the map at 37.136°, -116.069°.
Operation Plumbbob was a series of nuclear tests that were conducted between May 28 and October 7, 1957, at the Nevada Test Site, following Project 57, and preceding Project 58/58A.
Text from the Wikipedia article Operation Plumbbob, licensed CC BY-SA 4.0.