About 800 yards south of ground zero at Trinity Site, construction engineers built a heavy-duty 20-foot wooden platform. It had to be sturdy because they then stacked 108 tons of TNT on top of it.

A 100-ton explosive test occurred at Trinity Site on May 7, 1945, as a rehearsal for the atomic bomb test. The 100-ton test was largely unnoticed, unlike the July 16 atomic bomb test which was seen as ...