Seventy years after the United States resolved to beat Nazi Germany in the race to develop an atomic weapon, we know more about its Herculean effort to do so than ever before.  As of August 2014, the Department of Energy had posted the project's entire classified history online. Trinity Site—the very spot where the first nuclear bomb was detonated—will hold no-reservations-required open houses twice this year.

That said, we’re still a long way from fully appreciating the significance of the Manhattan Project—and in a special episode of Mysteries at the Museum, Don Wildman will visit the people and places most intimately associated with it. These are some of the records he’ll be reconsidering.

The Manhattan Project came into being after a group of physicists—including some, such as Albert Einstein, who had fled Nazi Germany—drafted a 1939 letter to President Roosevelt to warn him of the dangers of weaponized uranium, and to argue that America should try to harness the power of those chain reactions before the Germans did. That warning gained urgency after the U.S. entered World War II at the end of 1941, and in 1942, the project—code named for its research phase’s headquarters, in New York City—was underway on a vast scale.

When Brigadier General Leslie R. Groves—a member of the Army Corps of Engineers who had helped build the Pentagon—became director of the project in September of 1942, he constructed facilities to house research and development efforts across the country. The largest of these (above), where 75,000 people worked to produce enough Uranium-235 to create an atomic bomb, was in Oak Ridge, Tennessee.

At the same time, the theoretical physicist J. Robert Oppenheimer and a team of scientists in Los Alamos, New Mexico were struggling to determine how to fit the enriched uranium from Oak Ridge in a bomb that would be deliverable via airplane.

As Don Wildman will learn when he visits New Mexico, not all of the scientists on Oppenheimer’s team had the United States’ best interests at heart—but they weren’t the enemy we might have expected, either.

By 1945, the original $6,000 allocated for what became the Manhattan Project had ballooned into more than $2 billion in research and development. That effort had finally yielded enough radioactive material to build a bomb (which was assembled in this unassuming ranch house in New Mexico, above). A field test of the prototype was scheduled.

At half past five in the morning on July 16, 1945, atop a steel tower built to simulate the conditions of an aerial explosion, the first atomic bomb was detonated. A mushroom cloud extended more than 40,000 feet in the air, and the explosion’s blinding flash of light was visible more than 200 miles away.

By many metrics, the Manhattan Project was a success: The United States had successfully bent atomic energy to the cause of war. Dr. Oppenheimer’s response was more equivocal: He quoted a line from the Hindu Bhagavad-Gita, "Now I am become Death, the destroyer of worlds."

Though Germany had surrendered to the Allies in May of 1945, the war in the Pacific raged on against Japan. Ten days after the successful test in New Mexico, President Truman warned the Japanese that they would face “prompt and utter destruction” if they did not surrender. They did not—and faced with the task of ending the war as quickly as possible with as little loss of American life as possible, Truman ordered the bombing of Hiroshima. Three days later, he ordered the bombing of Nagasaki. After more than 200,000 people died in those blasts, the Japanese surrendered.

The largest and most secret project ever undertaken by the United States government helped end World War II. It also ushered in an era of covert, almost inconceivably expensive American military operations—and opened the door to the atomic age and the possibility of near-instantaneous global annihilation, once and for all.

Follow Don as he traces those consequences back to their origins—and decide for yourself if the price we paid was too high.

Watch the special episode of Manhattan Project: Mysteries at the Museum on Thursday, February 8 at 2 pm|1c.