On April 24, 1945, President Harry Truman received a note from Henry Stimson, his secretary of war, requesting an urgent meeting. Truman, who’d become president following Franklin Roosevelt’s death only 12 days before, had conducted numerous meetings like this as he tried to guide America through the end of World War II.

When Stimson arrived at the White House later that day, he brought U.S. Army Gen. Leslie Groves with him. Together, the two men briefed the president on a top-secret scientific program that was designing the first ever atomic bomb, a weapon they hoped could bring an end to the war.

The $26 billion program, code-named the Manhattan Project, involved nearly 130,000 people at locations across the country. As it happened, one of the crucial breakthroughs in the project took place years earlier at a humble college in Ames, Iowa.

Between 1942 and 1946, scientists at Iowa State College, as the university was then called, devised a method to produce pure uranium metal for the Manhattan Project, and eventually produced 1,000 tons of uranium for the war effort.

In 1937 Iowa State hired Dr. Frank Spedding, a renowned rare-earth chemist, as its new head of physical chemistry. At the time Spedding joined, the only other member of the department was Harley Wilhelm, a chemist who specialized in metallurgy.

In January 1942, Spedding was asked to join a top-secret group of scientists at the University of Chicago. The group, led by the famous physicist Enrico Fermi, was trying to use chain-reactions in uranium metal to create the first nuclear reactor.

Progress on the reactor was slow, however, due to a scarcity of uranium. Self-sustaining nuclear chain reactions can only occur in uranium that is free of impurities. This type of metal is rare in nature, and was especially hard to procure during a war.

Spedding, with his background in rare-earth chemistry, was tasked with finding a way to purify uranium from raw ore. However, after seeing the inadequate facilities in Chicago, he decided to begin working from Ames instead.

Upon returning to Iowa State, Spedding immediately hired his colleague Wilhelm, as well as several of their graduate students, to start designing a purification process.

Steve Karsjen, public affairs director at the Ames Laboratory, interviewed several members of team about their work.

“That whole process started right over in Gilman Hall,” Karsjen said. “I remember they talked about working 16-17 hour days and seven days a week there.”

While work on the purification process ramped up, Spedding went to Iowa State President Charles Friley to get official clearance for the Ames Project, as it was called, to take place on campus.

In a later interview, Spedding described how he approached the college president.

“Dr. [Friley] had to take me on faith because I told him we were going to do a very secret project, and that I couldn’t tell him about it,” Spedding said.

Despite not knowing any of the project details, Friley signed off and allowed it to go forward. At that point, Spedding began splitting his time between Ames and the metallurgical project in Chicago.

“That was no treat,” Karsjen said. “Because he would spend five days in Chicago and then get on the train and work all weekend [in Ames], then get back on the train Sunday night and go back to Chicago.”

In Spedding’s absence, Wilhelm led the work in Ames, all the while keeping his superior up-to-date on their progress.

“They would work all week, and then Spedding would come back on the weekends and would have what have been famously called ‘Speddinars’,” Karsjen said. “All the graduate students and everybody working on the project would come into a conference room and they would tell Spedding what they had been doing that week.”

Using this system, the Iowa State team spent the spring and summer of 1942 working to perfect the uranium purification process.

Sam Houk, a chemistry professor and analytical chemist at the Ames Laboratory, learned about Spedding and the process he underwent.

“Spedding and Wilhelm had a lot of experience purifying rare earth elements with the high-temperature procedures for making them,” Houk said. “Uranium has some similarity to the rare-earth elements, so [the procedures] were adapted to make uranium instead.”

In September 1942, the Ames Project finally succeeded in producing an 11-pound block of pure uranium. Spedding and Wilhelm personally delivered it to the metallurgical project in Chicago, where it was received with shock.

“[Their] eyes bugged out when they saw an 11-pound piece,” Wilhelm said. “They paid $10,000 for a two-pound piece and here they got this free of charge.”

By December 1942, two tons of uranium had been produced and shipped from Ames to Chicago, where it was added to the nuclear reactor, or “pile.” Finally, on Dec. 2, the scientists used the pile to successfully conduct the first ever nuclear chain-reaction.

Concealed beneath the stands of a small football stadium, the 431-ton pile operated for 28 minutes and produced just half of a watt of power.

Following the experiment, the Ames Project transitioned into full-scale production. To do this, work was moved out of the basement of Gilman Hall and into a small wooden storage building on the east side of campus. The building, nicknamed Little Ankeny after the nearby munitions plant in the town of Ankeny, was quickly installed with concrete floors and large induction furnaces for uranium purification.

Soon, 18 tons of uranium per week were being shipped from Iowa State to the Manhattan Project’s new secret reactor in Oak Ridge, Tenn.

“[Little Ankeny] was close to the railroad tracks,” Houk said. “So they actually built a separate spur of the track to it, and [the uranium] would be loaded with a crane onto these railroad cars and shipped out of here.”

Because of uranium’s enormous weight, each railroad car could only carry a small amount. This puzzled ordinary observers who watched the numerous empty-looking trains come and go from campus under armed guard.

“There was a tremendous amount of secrecy connected with this project,” Karsjen said. “Ames citizens speculated on lots of different things that might be going on there.”

More armed guards, stationed outside Little Ankeny itself, stopped anyone who got too close to the building. Even firefighters were blocked when they came to put out the many small fires that ignited at the facility.

Great lengths were also taken to make sure none of the workers shared any inside information. David Peterson, a student who worked on the project, shared one of the ways they were kept quiet.

“All of us that were of draft age were told that if we violated any of the regulations with regards to secrecy or security, we would be drafted and sent overseas to the front line,” Peterson said. “That was powerful motivation to be careful.”

At its peak, the Ames Project employed 500 people in uranium production and research. Eventually, two million pounds of metal were produced in secret for the war.

That secrecy was finally lifted on August 6, 1945, when the first atomic bomb detonated over Japan, leading to the war’s end. At last, the world finally knew the contributions of the Ames Project.

Harley Wilhelm later talked about what the moment was like.

“The first thing I did after the bomb was dropped was to call the wife and tell her to turn on the radio,” Wilhelm said. “That was the first time she heard about my work in three and a half years.”

For its two years of uranium production, Iowa State became the only educational institution ever to receive the Army-Navy “E” Flag. Gen. Leslie Groves, head of the Manhattan Project, personally presented the flag to the college at a ceremony in the Armory in October 1945.

The biggest recognition, however, came in 1947 with the establishment of the Ames Laboratory, the first state-operated and federally-funded research lab in the U.S. With Frank Spedding as its first director, the work of the Ames Project was seamlessly carried over to the new Ames Lab.

Houk said the lab would never have happened otherwise.

“[The Ames Project] began the concept of a laboratory here based on materials research,” Houk said. “Spedding managed to convince [the government] that these efforts should continue, and there would be long-term benefits both for nuclear technology and for other things.”

Currently, the Ames Lab cooperates with Iowa State to employ 745 people and conduct tens of millions of dollars of scientific research every year.

After the war, Little Ankeny was eventually demolished. Today, a boulder with with an inscribed plaque rests on the site. Located just south of Hamilton Hall, the boulder is the only physical marker of the pivotal role Iowa State played in ending World War II.