“We will probably never know the true extent to which William Laurence was co-opted, compromised, or corrupted by his military and governmental connections and involvements. It appears that in many ways, he was never really certain himself,” Mark Wolverton recently wrote in Undark. But from the very beginning, the story of the birth of the atomic age was being written by the very people who ushered it in.

In 1952—now the 10th anniversary of the experiment—the Kentucky New Era quoted Arthur Compton, the physicist who oversaw Fermi’s work, speaking at a luncheon of the Chicago Association of Commerce and Industry. (Compton was the one who spoke the words: “The Italian navigator has landed in the New World.”) Compton defended the use of the bomb, but he was more eager to stress the civilian impacts of the experiment, emphasizing energy as the War Department’s press release did:

As a scientific tool, the importance of the nuclear reactor is comparable with that of the cyclotron. As a means of improving health, it may reasonably be compared with the betatron, a new type of supervoltage instrument for producing X-rays and beta rays ... As a means of defense, I would rate the atomic weapons as comparable in importance with the airplane. But the great significance of nuclear energy seems to be as a source of useful power.

When the 25th anniversary came around in 1967, World War II was receding from memory and the Cold War had come startlingly close to turning hot. It was atomic weapons that Americans were thinking about again. Volney Wilson, another physicist who worked on the Chicago Pile, speaking to the Schenectady Gazette, was far less optimistic: “It’s been a big disappointment to me ... I would have thought that the development of this horrible weapon would have been more of a force to bring the world together.” Wilson was a pacifist who was always ambivalent about building a bomb, but his words now had a note of bitterness.

The 50th anniversary came at a more optimistic time: 1992. The Soviet Union had dissolved. The United States was the world’s only superpower. The Soviet Union was not only dismantling its warheads, it was selling them to the United States for electricity. “Highly enriched uranium from former Soviet weapons once targeted on our cities will be used to light and heat those same cities as fuel in American nuclear power plants,” William S. Lee, president of Duke Power, said at a November 1992 meeting of the American Nuclear Society.

But, it was not lost on journalists that this was still the atomic age. Articles written for the 50th anniversary note that Russia and the United States still had enough nuclear weapons to kill millions, and several other countries were pursuing their own. “Fifty years later, the legacy of the Chicago Pile remains mixed,” Earl Lane wrote in Newsday.

Which brings us to the75th anniversary of the Chicago Pile. Nuclear power is on the decline in the United States today. Nuclear weapons are ever present in the news again. Yet nuclear science has also produced real breakthroughs in science and medicine. The legacy of the Chicago Pile is mixed, and it probably always will be—until, and such is the nature of nuclear weapons, the day it is clearly not.