On this day in history - July 16th, 1945 - The first nuclear explosion.
In 1939, Albert Einstein and another prominent physicist sent President Franklin D. Roosevelt a letter that warned of Nazi Germany's fledgling program to build an atomic bomb. As a result of the letter, the top-secret Manhattan Project began, and the United States worked in earnest with an international team of scientists to build an atomic bomb before any other country could.
The Manhattan Project is one of the largest top-secret operations ever finished by the United States; it would have cost $26 billion in 2014. Plutonium and uranium enrichment facilities like Oak Ridge, Tennessee and Hanford, Washington were so large that entire cities were grown around them.
All of the resources from Oak Ridge and Hanford and the Manhattan Project were poured into yet another top-secret facility in Alamogordo, New Mexico at the Los Alamos Laboratory. Here Dr. J. Robert Oppenheimer led an elite group in the direct experimentation and creation of Trinity, the world's first atomic bomb.
It exploded at 4:45 a.m. on Monday, July 16th, 1945, a date that is now considered the beginning of the Atomic Age. After it detonated, Dr. Oppenheimer reported that he said "Now I am become Death, the destroyer of worlds."
A near duplicate of Trinity would be used on Nagasaki on August 9th in the Fat Man bomb.