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National Museum of Nuclear Science & History

Harold Riley was an American chemical engineer. After graduating from North Carolina State College, Riley began his career working as a rayon technician at the DuPont Company.

During World War II, DuPont was contracted to work on the Manhattan Project. Riley was one of the only DuPont employees informed of its secret mission. As Riley remembered, “Only the top people in each plant really knew about it. The executives swore all of us to secrecy and used every possible method to assure us how important complete silence was. I think it was a sense of pride as much as anything that made us keep still. We didn’t mention it to our families. My wife didn’t know any more about the atomic bomb than the next person.”

Riley would go on to work on the Manhattan Project at the University of Chicago, Oak Ridge, and Hanford. He would later recall, “It was a great day for all of us when that first atomic bomb was dropped on Japan. Our big reaction was to be glad we’d kept our mouths shut.”

After the war, Riley went on to receive D.M.D. from Tufts University and became a dentist. Riley died on June 30, 2013.

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