Answer: I believe you are talking about the world's first recorded nuclear explosion that took place on the plains of the Jornada del Muerto Dessert.
Explanation: It is to be noted that the Trinity site is still considered to be radioactive, and Trinitite which is a green glass-like substance is found abundantly in the area. Trinity was an atmospheric test conducted by the U.S. Army on July 16th of 1945. The site was chosen because of its isolated, flat grounded, non-windy lands. This experiment was so tightly gatekept that not even the military policemen whom rode with it knew of its contents.