Blaise Arena’s mother, Margaret (Shorgin) Arena, was a student at the University of Chicago in the early 1940s when a series of strange events occurred.

Rather suddenly, she told him years later, she began noticing construction near an old defunct football stadium.

Then, one day, she ducked into a nearby building to use a pay phone. She’d been in that same building many times before.

“And this time when she went in the door, alarm bells went off. And all of a sudden a sailor, as she put it, showed up and barred the way and asked her what she was doing here and asked her a lot of other questions,” Blaise says.

She realized later that she had accidentally stumbled into a secured building requisitioned by the Manhattan Project, the highly confidential government program charged with building the world’s first atomic bomb.

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The project had expanded into Chicago shortly after the U.S. entered World War II. There was a very real fear that American secrets would be discovered by the Germans, who intelligence officials then believed were working to develop their own atomic weapon. And so the project was conducted under a veil of secrecy.

It’s this secrecy that inspired Blaise to turn to Curious City with a question:

Did Chicago’s mayor know that an atomic experiment was happening on the South Side of the city? What about the school administrators? And exactly how dangerous was the project?

The answers to Blaise’s questions, Curious City has learned, provide a glimpse of an extensive apparatus of secrecy developed during this unique chapter in American history.

Why Chicago?

When you think of a nuclear test zone, you might picture desolate deserts and mesas, cordoned off by “No Trespassing” signs and patrolled by military guards. But at the height of World War II, before the world had ever seen an atom bomb, a vital step in the development of those weapons was conducted on the South Side of Chicago, on a busy university campus.

In 1942, the University of Chicago became host to one of the most influential science experiments in history — what’s known as the Chicago Pile-1.

Conducted in a squash court underneath the stands of Stagg Field, an unused football field, the Chicago Pile-1 was literally a pile of graphite and uranium. It stood more than 20 feet tall and weighed several tons. Under the careful watch of lead scientist Enrico Fermi, the pile was transformed into the world’s first self-sustaining nuclear reactor, laying the foundation for both atomic weapons and nuclear energy.

The project had originated in Columbia University, in the heart of Manhattan — hence the name — but relocated to Illinois in February 1942.

Upon first glance, the University of Chicago wasn’t the obvious choice. It was in the middle of a densely populated city — the second biggest in the country at the time — and far from military oversight in Washington.

But Dr. Robert Rosner, a U of C professor and member of the Bulletin of the Atomic Scientists, says military officials had their reasons.

First, U of C had a top-notch physics department, including Nobel Prize winner Arthur Compton, who would lead the Chicago chapter of the Manhattan Project.

In addition, planners believed that a location in the Midwest would be less susceptible to enemy espionage.

“The folks that were running the project, including the military, thought that New York was a bit too accessible for unfriendly folks,” says Rosner. “And so they thought we should move it into the heartland, away from the coasts.”

The squash court in Stagg Field, unconventional as it was, allowed the experiments to be conducted discreetly, but also in plain sight.

Who knew about the experiment?

Location was just one layer of the highly orchestrated security precautions. Secrecy was another.

William Nicholson was a young man just out of high school when he helped construct the Pile-1 in 1942.

“I was always aware that there was huge secrecy associated with whatever we did,” he told the Atomic Heritage Foundation in 2018. “It was drilled into us constantly by the leaders and by the security forces. There were known agents of the German government in and around the University of Chicago.”

Whether or not that was entirely accurate, the secrecy made it difficult for him to have a normal social life.

“We were told … that we were not to reveal anything of what you do. ‘Don’t take up with strangers. If you’re having a sandwich someplace or a beer or whatever, watch out that people who may engage you in conversation would be damaging to the war effort, that they may actually be the enemy.’”

The fear of Germany building an atomic bomb before the U.S. was pervasive. There was a very real concern that someone might figure out what Fermi and the other scientists were up to and report their ideas, successes, and failures to their German counterparts.

Rosner says the project was kept so tightly under wraps that Robert Maynard Hutchins, the president of the university, wasn’t entirely aware of what was happening.

“He might have had some vague notion, but I think it was probably an intentional lack of precision about exactly what was going on,” he says.

Rosner says that city officials, including Mayor Edward Kelly, were also kept in the dark.

“The political folks here in Chicago were not made aware of what was going on here,” says Rosner. “It was a secret.”

Other experts and memoirs from the time confirmed: The experiments were critical wartime secrets. The project administrators would not have taken the chance.

Although the Pile-1 experiment was conducted towards the end of 1942, the secrecy surrounding the project continued to be enforced through the end of the war.

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In the spring of 1945, the security apparatus was tested by a momentary breach at the school newspaper, The Chicago Maroon.

The paper had just published an article about its resident Nobel Prize winners, including Arthur Compton. The editor at the time — a freshman named Abe Krash — said he had no idea that Compton was anything more than a celebrated professor. That is, until two military officers showed up at the paper.

“The military had gone around the previous night and picked up every single paper throughout the campus and also gone to the printer and destroyed the plates,” Krash told the Atomic Heritage Foundation in 2017. “I was puzzled and didn’t know what we had done.”

The controversy centered around one line in that article — half a line, really — that mentioned Compton’s research on atomic energy. 

 It wasn’t until days later, when Krash was called to meet with an administrator, that he understood. The university was conducting top secret research for the war effort.

“‘They’re engaged here in developing a great new weapon, which will revolutionize warfare,’ that’s exactly what he said to me.” Krash said.

That line in the Maroon, as slight as it was, had triggered a swift response, proving that the security apparatus was still very much present on campus, more than two years after the experiment was complete.

How dangerous was the experiment?

In 1942, nuclear science was still largely uncharted territory, even for the eminent physicists with the Manhattan Project.

Although they had a strong hypothesis, they couldn’t have been completely sure of the risks posed by conducting one of the field’s foundational experiments in the middle of a crowded city.

Rosner says Fermi and the other scientists did create mechanisms to make sure that everything would go smoothly. They included adding and removing cadmium rods to the Pile, which could absorb neutrons and slow or stop the reactor.

“They had instituted some primitive but effective safety measures if something went wrong,” he says.

So, when it came time to take the Pile critical, Arthur Compton decided against warning U of C’s leadership. He later wrote in his memoir, Atomic Quest, “The only answer he could have given would have been no, and this answer would have been wrong, so I assumed the responsibility myself.”

But given what we know today about nuclear reactions and what the scientists did, Rosner says the public really wasn’t in any harm.

“Just to give you a feeling for it, the maximum output of this reactor was 2 watts — 2 watts is what your night light has,” he says. “This was not even close to being a bomb, it was not even a burp, this was not a very energetic structure.”

“Today we know that there really was not a risk. Whether it was fully understood at that time, I’m not so sure. I think they were probably taking a chance.”

The Legacy of the Chicago Pile-1

The Chicago experiment was conducted under extraordinary circumstances. But today, thanks in part to the atomic scientists themselves, this type of nuclear experiment would likely be subject to tight regulations.

After the war, many of the Manhattan Project scientists were concerned — and in some cases horrified — by the implications of what they had created. As one possible safeguard against nuclear proliferation, they advocated taking atomic research out of the hands of the military and putting it under civilian control.

The Atomic Energy Act of 1946 formalized this separation with the creation of the Atomic Energy Commission, which oversaw the expansion of the U.S.’s nuclear capabilities.

Today, those regulatory duties have been split between several government agencies. They include the Department of Energy and the Nuclear Regulatory Commission, or NRC, which specifically oversees and inspects nuclear research reactors at colleges and universities. It is a far cry from what happened underneath Stagg Field in 1942.

“The basic difference is, today’s technology is well established and regulated, and operated with transparency,” a spokesperson for the NRC said in a statement. “The Manhattan Project was experimental and under great wartime pressure, and of course top secret.”

More about our questioner

A retired chemist from Des Plaines, Blaise Arena says as a young man, he loved hearing about his mother’s brush with the early stages of the nuclear age.

“I think she had a strong place in her heart for this university, and I thought it was an interesting story and I had read of course about the events here on the Manhattan Project,” he says.

Of course, Blaise’s mom didn’t realize what she had stumbled upon in the early 1940s.

“I don’t know exactly what she thought [at the time],” Blaise says, “but she did say after the war she finally put two and two together.”

And what does he think about the fact that the project was so confidential that even the mayor of Chicago was kept in the dark?

“Science cannot be stopped, that’s the first thing. Secondly, they had to do it, and thirdly, if they didn’t do it, someone else is going to do it, that’s for sure,” he says.

Quinn Myers is a freelance reporter and producer. Follow him @rquinnmyers.