GWEN IFILL:Finally tonight, the tale of a top-secret town with a top-secret mission and the women who made history there.

Ray Suarez has our book conversation.

RAY SUAREZ:During the mid-1940s, thousands of young women got offers of good-paying jobs working on some sort of government project in the South. They were told their efforts would lead to a quicker end to World War II, but they were told little else.

They worked as secretaries and nurses, chemists and technicians, all the while not knowing the real purpose of their jobs: to enrich fuel for the first atomic bomb ever used in combat.

Denise Kiernan tells their story in the book "The Girls of Atomic City: The Untold Story of the Women Who Helped Win World War II." She's a journalist who has written extensive about American history, and joins us now.

Untold story, all right. I mean, whether it's Albert Einstein or Leo Szilard or Edward Teller or Robert Oppenheimer, even Harry Truman, this has been a man's story all along.

DENISE KIERNAN,Author, "The Girls of Atomic City: The Untold Story of the Women Who Helped Win World War II": It really has.

And it's also a story that's often told from the top down, from the position of knowing and decision-making down, as opposed to from the perspective of people who were crucial and invaluable to the success of the project, but didn't necessarily have any idea what the larger picture was.

RAY SUAREZ:Again and again, I had to remind myself while reading this book how circumscribed the lives of women were in 1943. You're reading it with your 2013 head. And then you have to remember, oh, yes, they couldn't do this. They couldn't do that in so many cases.

DENISE KIERNAN:In so many cases.

And at—in one respect, it was such a time of liberation for women, World War II, because so many men were away fighting. Opportunities opened up for them that had never existed before, to work in plants, to work with farm machinery, to work as welders. But, at the same time, you know, for example, Jane, one of the women I profile in the book, this was a very bright young woman who wanted to study engineering and was -- you know, just got a tap on the shoulder when she went to go matriculate at the University of Tennessee and was told, no, I'm sorry. You—girls don't study that.

But then she went on to be a statistician for the Manhattan Project. So, it was limiting and expanding at once, almost.

RAY SUAREZ:Cumulatively, your women give us a portrait of womanhood in America in 1943, some educated, some not, some rural, some urban, some of immigrant stock, some of longtime American stock.

It was really—the crowd you put together gave us a chance to look into all these different lives.

DENISE KIERNAN:And that was something that I really worked to do because I interviewed so many women.

And I, of course, interviewed a number of men as well who had lived and worked in Oak Ridge, Tenn., during World War II. And I did want to have as many perspectives as possible on this story. So, yes, some of the women are 18-year-olds with just a high school education recruited out of diners in Murfreesboro, Tenn. Others are, you know, nurses from Chicago, you know, with a certain amount of education.

And, you know, another is a chemist, you know, with a degree from the University of North Carolina. So I wanted to be able to show all of those perspectives and enter the story of the Manhattan Project from all those different points of view.

RAY SUAREZ:We are reminded again and again how peculiar this was, to bring together thousands of people from all over the place to a place that really didn't even exist yet.

It was like mushrooms coming up after spring rain. A city just comes out of the mud, all strangers to each other. But they couldn't talk to each other about what they were doing.

DENISE KIERNAN:Mm-hmm.

This was not a town that was designated or repurposed for the war effort. This was a town that didn't exist before the war. And they bring in all of these people. It started in 1942. The government thought, oh, we will probably have—let's plan for about 13,000.

Well, by mid-1945, less than two years later, a town with 75,000 residents, operating 24 hours a day, using more electricity than New York City, and with one of the 10 largest bus systems in the entire country, and it's not on a map. And, yes, you have all these people there together in this confined space spending all this time together, but the most natural question, "Well, what do you do?" is the one thing you're never supposed to ask.

So, "Where are you from?" was sort of the cadence you would hear everywhere, because that was safe. "So, where are you from?"

RAY SUAREZ:They were pioneering ways of refining radioactive material, weren't they?

DENISE KIERNAN:Yes.

The machines that they used to enrich uranium or separate different isotopes of uranium really had just been created just recently and had never been done anywhere near on this scale. So it was a completely—just a really completely brand-new endeavor.

RAY SUAREZ:They don't find out until the end what they were doing, when the bomb is actually detonated.

But did this experience change the life trajectories of these women? Did they go on to have different 1950s, 1960s, 1970s than they might have otherwise because they were in Oak Ridge?

DENISE KIERNAN:That's a very—that's a very interesting question.

One of the things that did happen to a lot of them is, you know, we were talking about before having all those people in such a confined space. A lot of people ended up married. So some women shifted over to being housewives. Others stayed in the plants working as chemists. One was—became a librarian for one of the plants. And she probably would have had a future as—you know, still working at that diner in Tennessee.

The young coal miner's daughter from Shenandoah always thought she would just be a secretary who got married and stayed in her hometown. And she saw a much greater part of the world because of that. So, a variety of opportunities, and perhaps what was most surprising for them was that this town that really didn't have any post-war plan, for many of them became home for now going on 70 years.

RAY SUAREZ:If you were a young adult in the mid-'40s, you're, what, in your 90s now? Just like World War II veterans who are disappearing from among us, are the girls of Atomic City also harder to find than they were just a short time ago?

DENISE KIERNAN:They are even just in the last several years.

And the window on this world—and, by that, I mean our access to this moment in time via the experiences and conversations we can have to people who actually lived through it—is shrinking so rapidly. The youngest of my girls right now is about 88 years old. And others are 94 and 96.

So there really is a limited amount of time, and decreasing every month the number of people we have that we can talk to about these experiences.

RAY SUAREZ:"The Girls of Atomic City: The Untold Story of the Women Who Helped Win World War II."

Denise Kiernan, thanks.

DENISE KIERNAN:Thank you very much.