The Secret City
The Manhattan Project
ORNL Today

Building the Bomb

In the year 1942 the nation was preparing for war, and this preparation included a secretive national project to produce the world's first atomic weapons.

Scientists had discovered as early as 1939 that uranium atoms could be split to release large amounts of energy in a process called fission. This discovery led to speculation that the science could be used for the development of atomic weapons, during a time period when it seemed vital to national security. Albert Einstein even sent a letter to President Franklin D. Roosevelt to inform the President that he and several other leading scientists believed in the potential of this application of the science to create weaponry.

By early 1942, scientists had developed two methods to produce the necessary fissionable material: one with plutonium 239 and the other with a highly purified isotope of uranium, uranium 235. Later a third method was added to large-scale production. Oak Ridge was a major contributor to all three methods. Three facilities were built in the Oak Ridge complex: Y-12, K-25, and X-10. Each performed separate functions in the project, which are explained in more detail under "The Manhattan Project," and the plans for building the city and the complex are discussed under "The Secret City."

Oak Ridge's contributions to energy research, nuclear science and ultimately building the atomic bomb made the city a major impact on the end of World War II and continues to make it a valuable resource for scientific advancement and research for the nation. Learn more about the continuing efforts of the Oak Ridge National Laboratories under "ORNL Today."

Visitors can learn more about Oak Ridge and its efforts in building the bomb by visiting the American Museum of science and Energy, attending the annual Secret City Festival, by taking a tour on the Secret City Scenic Excursion Train, or by exploring historic Oak Ridge by taking a driving tour with the audio supplement available at the Welcome Center.