The Manhattan Project

In partnership with the National Museum of Nuclear Science & HistoryNational Museum of Nuclear Science & History

Mary Lou Curtis's Interview

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Mary Lou Curtis's Interview

Mary Lou Curtis joined the Manhattan Project in 1943 and worked at the top-secret polonium production laboratory in Dayton, Ohio. Curtis developed new methods for counting and measuring polonium, which had only recently been discovered. In fact, it was Curtis who measured the polonium that went into the Hiroshima and Nagasaki bombs. She also discusses the difficulties of being one of the few women scientists to work at the laboratory.
Manhattan Project Location(s): 
Date of Interview: 
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Location of the Interview: 
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Transcript: 

[Many thanks to Bill Curtis for recording and donating this interview to the Atomic Heritage Foundation.]

Mary Lou Curtis: When I got out of college, it was 1932 and a big Depression was on. Miami University, where I graduated from, only placed one teacher that year because jobs were so hard to find. I didn’t get a teaching job that first year, but I worked in the Miami University Library for I think maybe thirty cents an hour and managed to get through the year.

Then I found this job in Richmond, Ohio where I’d taught for five years. Teaching is hard work because you are in contact with so many different personalities that you have to deal with, but I liked it. When I got married, I was automatically dismissed because they did not hire women teachers. The theory behind that was that men with families needed the jobs worse than single women. 

After we got married, Jack got a job in Dayton at the Wright-Patterson Air Force Base and I went with him. The baby was born in 1942, so I was pregnant when the war broke out. I stayed home and just took care of the baby. A part of that time, Jack had to stay out at the field because he was in the Army. He had been drafted. Then after he was drafted, he was sent to Georgia. I had to find a job, and I went to NCR. 

At that time, if you got a job with NCR you had it made. They told me that my qualifications were excellent for teaching, but that they were not excellent for industry. Somebody I knew at Summit Court [00:03:00], a pilot at Monsanto, was very close to Unit 3, one of the units that Niels had, the one that was working on the Atomic Energy deal. They were very close to where I lived. I could walk. I went there and I liked the place from the first time I walked in the door. It was just different. I had said that I could type, but my typing was nil. It was awful. So they gave me a typing test and said they were sorry, but they didn’t think they could use me, and I went home just crushed. 

The head of the thing, Dr. [James] Lum, called me and said, would I be interested in a lab job? Well I was interested in any kind of a job. So I said, “Yes.” That’s when I started. 

It was hush, hush work. We couldn’t tell anybody what we were doing, but it was in the field of radioactivity. In my physics textbook there was one chapter on radioactivity at the end of the book, so really this was a brand new field. A lot just wasn’t known. 

I went into a lab immediately, and this developed into what we called the “Counting Room.” We were counting particles or X-rays that came off of radioactive material, and we had to determine the purity and the amount. I developed techniques for doing this. There were not instruments available at the time, and we had an Electronics Department that developed our own instruments. My job was to find methods for analyzing materials, and that’s what I did for a long time. 

The job just grew and grew, because I remember when I went there and they interviewed me they said, “This is a routine job. It isn’t a field that you can get ahead in.” But I wasn’t interested in getting ahead; I was just interested in getting through until Jack got out of the Army and could support us again. My father told me, “No job is necessarily a dead-end job. You can make something of it.” 

It was a real rugged two years because the grocery stores weren’t open after six o’clock, and I would have to pick up Jane whenever I was leaving [00:06:00]. Later I left her at Warren Nurseries. They would take care of them for fifty cents a day, including their breakfast. So that’s where Jane was all that time.

I had one supervisor; his name was Sergio DeBenedetti. He was an Italian Jew, and we just loved him. He was fun. He had escaped from Mussolini’s Italy on a bicycle, and he had worked at the Fermi Institute. He never wanted to do the same thing twice. Once he’d worked out a technique, he never wanted to have anything to do with it again. He wanted something new and more challenging to work on. He was quite a guy. 

They said never to use the term outside of this lab of “the Manhattan Project.” Arthur Compton came and talked to us, all of the technical people, all of the chemists and others. The girls that worked for me in the Counting Room weren’t invited, but I was. I would say there were only about twenty-five of us, which was a small group at the time. And Arthur Compton was one of the head men and one of the promoters of nuclear research, the bomb as it turned out. We didn’t even know what the people in the next lab were doing, it was so secret. Arthur Compton told us, “What you’re working on is in the way of a secret weapon. The Germans are working on it too, and whoever gets it first will win the war.” 

We worked every day but Sundays. We worked six days a week regularly, and all holidays except for Christmas. That was the only holiday we got off. It was in the old Gracie Green School, which had been deserted as a school and Monsanto went in. The first winter we didn’t have any heat in our lab and it was pretty darn cold. Everybody had colds. In the summer all of the windows were sealed shut and we had no air conditioning. 

I complained because the way that the floor plan was, if there had been a fire there would have been no way we could have gotten out. The people next door had access to the outside. So their solution to the thing was to cut a hole about this big. We had one girl that was so heavy, she’d have gotten stuck if she’d tried to get out that way. They cut the hole between the two labs. 

Polonium was used in the trigger for the bomb. I actually measured the material that went into the first bomb, the one that was dropped in Hiroshima and also the one that was dropped at Nagasaki. We separated the polonium from bismuth. The actual work of doing the separation was in that building in Oakwood in somebody’s home, somebody’s playhouse. I think it was the Talbot’s playhouse, and they had commandeered it. The neighbors were really put out with Monsanto. It was a squash court that they had. It was a playhouse in Oakwood, and the government took it over for this work. 

What they did was to separate polonium. Of course the place got hot, radioactively. And it was quite an effort to clean it up after we were through using it for the bombs. They’d bring me small samples and they would know they could dissolve it only so much. So they would put it on slides and bring it in and we’d measure it. They developed the instruments for measuring it. We had an Electronic Department that built it. At the time you couldn’t buy the instruments to do all of this. They weren’t commercially available. Joe Hyde, who you’ll remember, was head of the Electronic Department, and they developed all of the instruments that we used for a while until it became commercially available. 

As we got different materials to work with or different radioactive elements that we were interested in, I had to develop the techniques for measuring it. Once the techniques were developed and proven, then the girls in the lab did the actual counting work. But I had worked out the procedures first. They’d bring me small samples and they would know they could dissolve it only so much. So they would put it on slides [00:12:00] and bring it in and we’d measure it. They developed the instruments for measuring it there until later when all of this sophisticated stuff was manufactured commercially.

The work began to get a lot more complicated. Right at first, when we called it the Counting Room, we only had measured the amount of activity coming. So that gave you, if you knew how fast the material was disintegrating, how much you had, how much material was on that actual slide that they gave me to measure. Afterwards we branched out and we started measuring gases and doing energy determinations. By energy determinations, you knew that you could identify the particular materials that were on the slide, because they all had a different energy pattern. 

One of the units of Monsanto in Dayton was the Center Research Facility. There wasn’t any place for us to eat lunch where I worked, which we called “Unit 3.” So we piled into this station wagon and you never knew whose lap you were going to be sitting on. We were piled three or four high it seemed to me, and that’s how we got lunch every day. But you got to know people pretty well.  Unit 1 didn’t work on Saturday, so all of the girls that were in on this decided that on Saturday’s all of us would bring something and we’d have lunch.

Interviewer: A potluck type of thing? 

Curtis: Yeah. That went on fine until one day the girls who brought in the food decided we’d have waffles. They brought in the waffle irons, and of course the smell of the waffles lofted through the building. Dr. Lom called me in and said that since not much was known about the physical effects of this, that it would be better if we didn’t eat in there. We should not eat in the laboratory, but we could have the station wagon to go to lunch wherever we wanted to. 

They had GIs working there, and they weren’t allowed to tell. One of the boys, a real character, got arrested for [00:15:00] speeding or some traffic violation. He was locked up overnight until they could get in touch with somebody to exonerate him. They’ve now given the building to Ohio University. 

I remember when the bombs dropped, we were still in our location in Dayton. We were standing in the cafeteria line and somebody came in with a newspaper with the headlines, “ATOMIC BOMB DROPPED ON HIROSHIMA,” or words to that effect. This was when people were beginning to feel guilty about having dropped the bomb, but I never felt guilty about that because in the first place I had two brothers in the service and my husband and Tinker’s husband. There was the fact that that had ended the war and thousands of lives were saved on both sides that would have died if we had to have invaded Japan. So I think that we saved lives. 

Then afterwards for a long time we were the only ones that had the bomb and we didn’t use it for aggressive purposes. The only time it was used was to end that war, which was not of our making to start with. 

I guess I was an expert on measuring radioactive materials, particularly alpha-emitters. I published about twenty things in scientific journals about different ways of analyzing things. One of them for instance was on plutonium. They used that in the bombs and in the weapons. It had to be free of a plutonium isotope called plutonium-236. With time it got more radioactive, and so if they used it in an artificial heart for instance the amounts of plutonium-236 would be too dangerous. 

So I developed a method of determining parts per million quantities of plutonium-236 and 238. There was another group working on it too, and we finished about the same time. I didn’t know that anybody else was working on it too. They [00:18:00] accomplished the same thing, but they had to wait two weeks for the stuff to grow in, and I could give them the results right away. They were furious and they blamed me. Amos, who lived across the street here, called me and asked me if I could do it and I said, “Yeah, I thought I could.” So he knew I was doing it, Rand knew I was doing it, but this other group was so mad. They gave their paper and had a footnote that there was another method.

Interviewer: That took less time?

Curtis: No, it didn’t say that. 

It was a handicap being a woman, but I took it for granted that that’s the way it had always been. And I know that I had to be better at what I was doing than any man that wanted my job. But Monsanto was a wonderful company to work for I realize that now more than I did then. I hear of things happening at other places. When I got my twenty-five year recognition, for having worked there twenty-five years, the plant manager, who gave me my watch said, “I think it’s significant that you accomplished what you did before the days of women’s lib.”