Oppenheimer — United States
The Trinity test on 16 July 1945 — the world's first nuclear detonation — witnessed by the scientists who built it in the New Mexico desert, 21 days before Hiroshima.
The Trinity test used a plutonium implosion device ('The Gadget') detonated atop a 30-metre steel tower. The explosion yielded approximately 21 kilotons, creating a fireball 40 km high and a crater 1.5 metres deep in the desert floor. The site, now White Sands Missile Range, is open to the public twice a year. It was designated a National Historic Landmark in 1975.