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Inside the Secret Cities That Created the Atomic Bomb

The Manhattan Project, the program that developed the first nuclear weapons during World War II, worked out of three purpose-built cities in Tennessee, New Mexico, and Washington state. An exhibition considers their design and legacy.


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Photo Courtesy of the U.S. Department of Energy and the Oak Ridge Public Library

Built by the U.S. Army Corps of Engineers at rapid speed beginning in 1942, the instant wartime cities of Oak Ridge, Tennessee; Hanford/Richland, Washington; and Los Alamos, New Mexico, revolved around military research. They held laboratories and sprawling industrial plants, but also residential neighborhoods, schools, churches, and stores—war workers had personal lives and families, after all. At their peak in 1945, the three cities had a combined population of more than 125,000.

Their research facilities later morphed intonationallaboratories. But during the war, none of the cities appeared on any maps: They were the top-secret centers of the Manhattan Project, the U.S. military’s initiative to develop nuclear weapons before the Nazis got there first. The project achieved bitter success in August 1945, when the U.S. dropped atomic bombs on Hiroshima and Nagasaki in Japan, instantly killing 150,000 people. Japan surrendered several days later, effectively ending the war, although historians still disagree about whether the use of nuclear weapons hastened the end.

Secret Cities, a 2019 exhibition at the National Building Museum in Washington, D.C., explored the architecture and urban planning of the Manhattan Project sites. Their design was driven by unique  considerations, such as including buffer zones for radiation leaks or explosions. But in many ways, they looked and felt a lot like other American towns of the mid-20th century.

Curator Martin Moeller argues that the cities reflected the broader architectural interests of their era, such as prefabrication, and that their legacy can be felt in postwar suburbs and even Park Avenue skyscrapers (via the architecture firm of Skidmore, Owings & Merrill, or SOM, which oversaw Oak Ridge’s design). Moeller talked with CityLab about the exhibition.

How did you first learn about and become interested in these cities? I think you mentioned there’s a family connection?

My husband grew up in Oak Ridge, and his father was a nuclear physicist at the Oak Ridge National Laboratory. Now this, of course, came long after the war. My first visit to Oak Ridge was in 1985. That’s when I met my husband. I was meeting his family for the first time, and I remember driving into the city and at first thinking, “This kind of feels like a town in the Appalachian region of Tennessee.”

And then it wasn’t long before something struck me as being a little strange. The more I visited the city, the more I realized there were lots of things that were funny. At some point early on, I learned of SOM’s role in designing the city and laying it out. I kept learning more and more about that and realizing the scope of that gradually over time. So literally for more than three decades, at least in the back of my mind, this has been an idea for an exhibition.

The Manhattan Project was a high-risk enterprise. What kinds of spaces did that require, and what did planners do to keep people safe, not only in these cities, but outside them?

It starts with the site selection. That was a very critical aspect of the decision to locate these facilities in Oak Ridge, Los Alamos, and Hanford. In each case, there were natural features, topographical features, that were considered to be favorable. In all three cases, they were somewhat remote—in the case of Hanford and Los Alamos, very remote—which offered a more secure environment, of course. But also, in the event of a disaster, an explosion or a radiation leak, that would also minimize the potential exposure of people outside the project to any sort of radiation danger.

The activity to build and run these facilities was mind-boggling in scale. The camp for construction workers at Hanford, Washington, ultimately housed upwards of 50,000 people, making it the fourth largest “city” in the state. Photo Courtesy of the U.S. Department of Energy, Hanford Collection.

Within the sites, to some extent it had to do with just space, particularly at Hanford, which is a very large, flat plain right along the edge of the Columbia River. That expanse of land gave them the opportunity to isolate these sites from each other—just the sheer distance. Oak Ridge is defined by a series of ridges, and they deliberately sited the main facilities in three different valleys, so that if there were any kind of leak or explosion, the natural ridges around that facility would tend to contain that.

As a secondary concern, if German bombers had managed to penetrate that far into the United States, there was a thought that it would be harder for them in a single bombing run to take out more than one facility [at Oak Ridge], simply because of the separation and the ridges between them. So those things were all baked in just from the start, based on the selection of the site.

In many ways, the industrial facilities—the actual key work [spaces] of the Manhattan Project—are kind of the least interesting, architecturally. Some of them are interesting just by virtue of their scale and proportions. There was the K-25 plant at Oak Ridge, which was where they enriched uranium using the gaseous diffusion method. When it was completed, it was the largest building in the world under a single roof, spanning more than 40 acres.

Aerial view of the K-25 plant, Oak Ridge, c. 1945. The K-25 plant was built for the enrichment of uranium through gaseous diffusion, in which gaseous U-235 was separated from U-238 through an incredibly fine mesh. The process was extremely space-intensive. When completed, K-25 was the largest building in the world under one roof. Photo from the National Archives and Records Administration.

So really, the main story of architectural interest involves the housing and the civic buildings, and commercial buildings, and schools. That’s where there [is more] interest, derived from several things: first of all, in Oak Ridge, largely from prefabrication and semi-prefabrication, [such as] the “Alphabet Houses” that SOM designed. Also the layout of the communities and the incorporation of green space.

Not to say that those [Alphabet] houses were necessarily stunning works of architecture, but SOM really kind of threaded the needle there. [The architects] knew that their task was to create something that felt homey, but also felt reasonably modern. So they’ve got the pitched roofs and casement windows, but their proportions, their simplicity, kind of prefigure the early postwar suburban house without actually pushing the envelope in terms of design.


A “Flat Top” house in Oak Ridge, 1944. One of the most common houses in Oak Ridge was this B-1 model, commonly known as the Flat Top. (Other Alphabet models had pitched roofs.) Each of these houses was built in a factory and transported by truck in two or three pieces to the site, where it was assembled atop a foundation. The architectural firm of Skidmore, Owings & Merrill (SOM) oversaw the planning of the city and the design and construction of most buildings within it. Photo from the National Archives and Records Administration.

As SOM continued to work in Oak Ridge after the war, that’s when they really started to become more and more cutting-edge with their designs. For example, the new senior high school that was built post-war was this beautiful, elegant structure, very glassy, [with a] rational layout, really picking up on a lot of things that we would associate with high Modernism, and pushing that envelope a little bit.

People who know the name “Skidmore, Owings & Merrill” probably associate it with Lever House or other skyscrapers the firm designed. How did it come to build a nuclear city for the government?

It was a very logical progression. SOM had its start in the 1930s. Both [Louis] Skidmore and [Nathaniel] Owings had done work for the Chicago World’s Fair in 1933 and ‘34. And they built on that and actually managed to do pretty well during the Great Depression, getting a good number of commissions, including at the ‘39 to ‘40 World’s Fair in New York.

During that time, they had also done some work for the John B. Pierce Foundation. This was a group that had been founded by a guy in the building industry, specifically to support and promote research in building technology, and housing in particular. SOM had designed some experimental houses for the foundation using different materials and, as you might expect, trying to maximize space and simplicity and value.

After World War II was already going on in Europe, and there was a really good chance that the United States was going to be entering the war one way or another, a lot of the military-industrial complex was gearing up. That included the Glenn L. Martin aircraft company. [The company was] building or expanding a plant outside of Baltimore in a town called Middle River and needed housing for a huge number of employees. They approached the John B. Pierce Foundation and said, “Can you help us?” And Pierce brought in SOM.

That’s when SOM first had an opportunity to design an entire town of sorts, using a semi-prefabricated construction system. And I say “sort of a town,” because in this case it was really purely residential. They were designing prototypes for houses that could be built very quickly, and assembling a nice little residential neighborhood.

That’s why I argue that Oak Ridge was significant, as a real, complete new town, with shopping and schools and churches and everything, that went beyond most of anything that had come before. This was a new endeavor of trying to plan an entire city, not just neighborhoods, and not just a commuter suburb. And so SOM was faced with some interesting challenges—like, how many businesses of certain types did they need?

Initially, the target population for Oak Ridge was about 13,000. One of the partners—I believe it was Skidmore—had a hometown in Indiana with a similar population. So they simply went there and counted how many beauty parlors there were, how many markets, how many drugstores. It was like, “Well, that’s probably a good measure for what we’re going to need for an equivalent city in Tennessee.” To me, it’s a classic [example] of architects figuring out how to solve the problem.

It’s interesting that women were an important part of the workforce in these cities, but at the same time, the cities were sharply segregated by race. Would you say they were microcosms of American society at the time, or were they socially different?

Both, in my view. I think the fact that segregation was a given represented the realities of the day. There was a lot of progress being made because of the exigencies of the war, and people who had certain skills and talents were being used more than they might have been before. Still, the assumption was that African-Americans were not likely to be having those skills and talents.

There were a couple of African-American scientists and engineers. They faced real challenges, but they did manage to get through. There were some women scientists and engineers, but they were few and far between.


African-American women hanging laundry in a “hutment” area, Oak Ridge, 1945. The secret cities of the Manhattan Project treated racial segregation as a given. In Oak Ridge, many African-American workers and some white workers lived in plywood “hutments.” The contrast between these crude, ill-heated huts and the comfortable housing built for most white workers was stark. Photo by Edward Westcott, from the National Archives and Records Administration.

I think probably more so than in the society at large, there were some meritocratic tendencies [in the cities]. The likes of Oppenheimer [J. Robert Oppenheimer, the physicist who was technical director of the Manhattan Project] and so on, if they saw that someone had a necessary ability or skill, they would do their best to find a way [to use it]. Think of the movie Hidden Figures.

It’s hard to know if any of these towns were really ahead or behind. My guess is that they were pretty much in line with the rest of society.

The dropping of nuclear bombs on Hiroshima and Nagasaki had a horrific human toll, as the exhibition makes clear. Most of the people in the secret cities hadn’t known their work was part of a program to develop nuclear weapons. How did they react when U.S. forces dropped the bombs that they had unwittingly helped create?

I really tried, in a small number of quotes [in the exhibition], to capture that range, because it was a range. There were people who jumped up and down and celebrated at what they thought was the end of the war, and they felt that they were justified in that view when Japan surrendered. There were others who were devastated, absolutely devastated.

One of my own colleagues, it turns out her parents were both at Oak Ridge, and they were very much in that position. They were working on this, and they did not know what they were working on, and when they found out, they were absolutely horrified.

There were more complex reactions in between. There were people who were relieved, but sobered by the news of what happened. It also took a long time [for news] to get out of what really happened. So the initial reactions may not have mirrored subsequent reactions as people learned more and pictures of some of the victims came out. It was very complex.

Do you think it would be possible for the federal government to build secret facilities on this scale today? I think about how much more locatable and surveilled we are, with cameras and GPS and drones. How long would they remain a secret?

I just can’t imagine it. I mean, during the Cold War, the Soviet Union had its own versions of secret cities, which were in some cases huge. The question there is: secret to whom? Most of us growing up in the United States didn’t know about them, but I’m quite certain our government did because we had spy satellites.

Los Alamos main gate, c. 1943. Anyone approaching Los Alamos during the war had to pass through at least two checkpoints. Photo Courtesy of the Los Alamos National Laboratory Archives.

There were spies in Los Alamos and other places, so there were a few forces in the Soviet Union and elsewhere who knew about the secret cities even during the war. But I certainly think, by and large, they managed to keep the secret remarkably successfully.

Now, as you say, [we have] drones, let alone just Google Earth or Google Maps. I love maps and I love geography, so just for fun I’ll browse around on Google Maps and see what I find. Particularly around Washington, every so often you’ll see something that’s been fuzzed over. Usually it’s one building or a part of a building. It’s not going to be a city of 75,000 people.

Someone’s going to be snapping pictures, and someone’s going to be flying a drone over it, and someone’s going to hear something. I just can’t even imagine that it could happen [today] at that scale.

Amanda Kolson Hurley is a senior editor at CityLab.

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This post originally appeared on CityLab and was published May 10, 2018. This article is republished here with permission.

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