Explore the top-secret American project to build the world's first atomic bomb.

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In a This Day in History video, learn that on July 16, 1945, the United States conducted the first atomic bomb test in the New Mexican desert. The test was the culmination of three years of secret planning under the codename, The Manhattan Project. Scientists, soldiers, and officers assembled the observation huts, some as far as 10 miles away from ground zero. There was an intense flash of light, and then the a-bomb produced a fireball that expanded nearly 2,000 feet in two seconds; it boiled up into a mushroom cloud nearly six miles high.