Nuclear Museum Logo
Nuclear Museum Logo

National Museum of Nuclear Science & History

Edwin McMillan’s Lecture

Edwin and Elsie McMillan were among the first people to arrive at Los Alamos. Edwin, who would go on to win the Nobel Prize in Chemistry, was involved in the initial selection of Los Alamos. In this lecture, Edwin describes visiting Jemez Springs and Los Alamos when he, Oppenheimer, and General Groves were deciding on the site for the weapons laboratory. McMillan also discusses his involvement in implosion research, the gun program, and recruiting scientists including Richard Feynman to the project at Princeton University. He also remembers requisitioning Harvard’s cyclotron for the Manhattan Project.

Date of Interview:
September 12, 2022
Location of the Interview:


Edwin McMillan: Ladies and gentlemen, I would like to start with two remarks. First, this is going to be a personal story, so if I use the first person singular, this is not pure egotism, it is simply the fact that that’s the part that I know best. Second remark is, the difficulty of establishing facts at such a late date, even of important things. During the Manhattan Project, of course, there was security impressed upon everyone, so very few people kept any notes. We did not keep diaries or little black books with all the records of where we had been and what we had done. I have found that even other people had the same difficulty of remembering. So, trying to establish detailed facts turned out to be quite an interesting thing, and some of that may come up a little later.

I gave this a title, “Early Days,” and when I finally got the thing organized, it turned out early days extend previous to the establishment of Los Alamos. There is a pre-history as well as a history. I chose the two dates, September 14, 1942, to begin with, and September 17, 1943, almost exactly a year later, to end with. I know there are certain incidents that happened on those dates to establish them.

The first date, I was at the U.S. Navy Radio and Sound Laboratory in San Diego working on sonar when I got a telegram from Arthur Compton at Chicago, asking me to come to a meeting one week later to meet with [J. Robert] Oppenheimer and John Manley, [Enrico] Fermi and others, the telegram says. I have to admit I can’t remember who else was at that meeting. I am sure Ernest Lawrence was there and there were others, but those names were in the telegram so I have them down. Things that happened just to have been put into a message get remembered.

In between my receipt of that telegram and my attendance of the meeting a week later, a very important thing happened, which might be a better starting date. Namely, on September 17, exactly one year from the ending date, General [Leslie] Groves joined the project. He was asked to take over. The Manhattan Engineer District already existed, but he was asked to take over and consented to do so.

At this meeting in Chicago, I decided I would join the project. I had already been approached by Lawrence in Berkeley, who wanted me to come and help him in his isotope separation work. I had begged off on that at least for a few months until I finished a project I had going at San Diego. But learning about the other ramifications of the project and the starting of a new lab, that was very attractive to me. Also, I say that Compton wanted me to come to Chicago and work with him. The new laboratory was the magnet that drew me, something somewhat adventurous. I decided to join the project.

Then, shortly after that—I can’t give you exactly when—I moved from San Diego to Berkeley and my wife moved up with her parents in San Marino. I spent the next two months in Berkeley working with Oppenheimer and [Robert] Serber, and a number of people came and went during this period.

My office in LeConte Hall at the university, UC Berkeley, 325 LeConte Hall, was the organizing center for the laboratory. In that office we were making plans, rather, you might say preliminary plans. But also some things had to be done in more detail, for instance, the obtaining of equipment. I should also say that John Manley during this same time was working for a base in Chicago and was also involved in this planning. I find some correspondence between myself and Manley which ties that down.

We had to decide what equipment was needed, think about personnel and also buildings. One has to have some idea of what laboratory buildings are needed. I also found some dates that in early November there was a Colonel [John. H.] Dudley, who was attached to the Army Engineers. He and General Groves, who was by then already well established in the project, came to Berkeley and met with us. They were talking principally about the sites and the buildings that would go there. I remember looking at many architects’ plans as to what was being suggested as to how things were to be arranged.

As of this time, this was November 1st and 4th for these two visits by Dudley and Groves, the site had not been chosen. There were certain requirements for a site. It had to be far from the borders of the Unites States and it had to be in an area not close to highly built-up areas, mainly for security reasons. Didn’t want to have the scientists mingling with a lot of townspeople and gossiping about what they were doing. Many places were looked at. Colonel Dudley, now General Dudley, will speak to you as the last one of this series, and I don’t want to steal his thunder. But some of the information I did get from him, and he said that he visited most of the small towns in the Southwest. He said he traveled thousands of miles on two-lane roads, one lane for the left wheels and one lane for the right wheels.

Well, this site search headed up. Colonel Dudley had decided on the basis of the criteria and what he had seen, that the best site was Jemez Springs, New Mexico. It was arranged that Oppenheimer and I were to go to Jemez Springs. We were supposed to get horses and General Dudley, Colonel Dudley at that time, was to meet us and ride the boundaries. The idea was to see whether the security was adequate, where the fences would be put and all that kind of thing, and also look at existing buildings and the general adequacy of the site. So we went there.

Now, the date of this thing took a lot of research to find out, because nobody remembered when it was. It finally got tied down. General Groves found his diaries; he did keep a diary and located it. Colonel Dudley had turned over all of his records to the War Department and they had been put in the archives. Then at some time in what is called a “reduction in volume of records,” they were all destroyed, his personal logs of where he had been were all destroyed. That was sort of a tragedy. Then he discovered that he had some boxes, he had kept a few things out like travel vouchers and stuff like that. From those boxes, he was able to find dates of where he had been various times, and that confirmed this date. He confirmed Groves. It was November 16, 1942. But as far as I was concerned, my memory, all I could say was around the middle of November. That was just as close as I could get.

We went up to Jemez Springs and we met Dudley there. I will describe a little bit of the topography there. It is in a canyon. It is a canyon that runs westward out of the Sangre de Cristo Mountains. I’m sorry, not that, but the next range west. It’s a deep canyon with a flat bottom. It’s got a river and a road and a little bit of land, sort of a one-dimensional site. It didn’t seem to me that there was room there, and I imagined a community all strung out like that. It seemed very awkward, and I expressed considerable reservations about this site. Of course, Dudley was supporting it very strongly, because it was his choice. And it was, I suppose, the only one that really met all the criteria exactly.

Well, for one thing, we couldn’t ride the boundaries. That was impossible, because that’s way up on the canyon. It would be several days’ work to get around that thing. I’m not even sure you take a horse around there. We were arguing about this when General Groves showed up. This was planned. He would come in sometime in the afternoon and receive our report.

One thing I remember, which is sort of a little personal touch, is that Groves, his arm was asleep. He had gone to sleep on the plane. He flew out overnight and had gone to sleep, and his arm hadn’t waked up yet. He was miserable with this dead arm. Well, soon as Groves saw it [Jemez Springs], he didn’t like it. There was no argument there. Groves said, “This will never do.” So I never had a chance to make my fine arguments about it.

At that point, Oppenheimer spoke up and said, “Well, if you go on up the canyon, it comes out on top of the mesa and there’s a boys’ school there, which might be a useful site.” We all got in cars. We didn’t ride horses. Some people have said we rode horses there. That’s too far. We went up to Los Alamos Ranch School.

I remember arriving there, and it was late in the afternoon. There was a slight snow falling, just a tiny drizzly type of snow. It was cold, and there were the boys and their masters out on the playing fields in shorts. This is really a place for hardening up the youth. Soon as Groves saw it, Groves said, “This is it.”

I have a copy of a letter here, which I got from Groves, writing to establish some of these— particularly this date. I thought I would read just this one paragraph out of the letter. “I think it perfectly correct to state that there were two decisions made on this trip. The first was turning down Jemez Springs. The second was the selection of Los Alamos. I had no intimation before turning down Jemez Springs that Los Alamos was a possible site. I’m not sure whether you and Dr. Williams accompanied us to Los Alamos, but I think you did.” There’s a failure of memory there. Dr. Williams, that would be John Williams, was not on that trip. See, it just shows how untrustworthy the best people are when it comes to memory.

As soon as the site was chosen—within just a day or two, I think it was the next day—a site report was authorized so they could make the official investigation and arrange for the acquisition and so on. This went through rather quickly and the site was acquired. I believe that the ranch school was not in great financial condition anyhow, so there was no reluctance to sell. That’s how Los Alamos got to be the site.

Then, of course, it turns out I went on to Washington with Oppenheimer. We had some discussions there and came back, and four days later, actually went into Los Alamos. The first time, nobody went in, we just stood outside. As I remember, we looked at it, went and looked it over. At that time, it was Oppenheimer, Ernest Lawrence and myself on November 20th, on that trip. We were among the first to see this site.

Of course, Oppenheimer knew it already, having a ranch in that area, in the Sangre de Cristo Mountains. He had been over and seen the school before and knew about it. I think Oppenheimer privately wanted that site anyhow, but he didn’t put it forward until this time. Other stories I’ve heard was that Los Alamos had been chosen all the time, and this was just an exercise. But I think Groves’ statement that he had not heard of Los Alamos as a site before would put that one down.

Objections to Los Alamos were it didn’t have mountains around it, so you couldn’t have a high fence that people couldn’t get over. But on the other hand, it was on top of a mountain, or rather a mesa, which is just as good. There were other objections such as roads, water, and so on, but they were not fatal and were overcome.

Continuing the story, later in 1942, and these dates I have lost completely. There were many things going on, not only the planning, ordering equipment. I remember writing out orders for a large set of machine tools to set up a large shop, something I really didn’t know much about. But I had the advice of the shop men at Berkeley and somebody had to do it, so when the shop was there the tools would be ordered. There was a long lead time on some of these things.

Another thing I remember was recruiting. I was asked to go to Princeton, where Robert Wilson had had a group working on a method for separating isotopes. I was the recruiter, and I went out to Princeton and talked to these people and recruited essentially the whole Wilson group. That must have been about on the order of twenty people or so: Bob Wilson, and including Dick Feynman. So I recruited Feynman to the project.

Another thing I recall was a trip around the country to laboratories that had cyclotrons, to choose a cyclotron for the project, because they had to get nuclear equipment. I went to several laboratories that had cyclotrons the right size. The one that was the best suited, best condition and so on, portable—as close as a cyclotron gets—was Harvard, so I recommended Harvard. The Harvard cyclotron was taken, and for many years after that some people at Harvard were very angry with me. They would say, “You stole our cyclotron.” But then the cyclotron did very valuable work at Los Alamos, so I think it was worthwhile.

The next item down here is the actual arrival at Los Alamos. Of course, in the meantime, construction was going on, housing, laboratories, and so on. Elsie will tell you about some of that stuff. The date I found for the arrival of Oppenheimer and his immediate staff was March 15, 1943, in the middle of March. Oppenheimer was there and a number of people like, perhaps twenty or so, these numbers I don’t remember. I followed very shortly after that. That date I do not have and probably will never be able to find. Mrs. McMillan came on April 1, so that from April on we were a going concern and the laboratory was building up, people were arriving, equipment, buildings and so on.

I wanted to talk about a couple more items here, specific programs. I was connected in a small way with the early stages of the implosion program. You know there were two methods of bomb assembly that were worked on. One was called the gun method, which consisted of simply firing two chunks of fissionable material together at high speed and then releasing some neutrons to start the chain reaction.

The other was the implosion program, where you have a converging explosive wave that simply pushes material in from all directions. That would have the advantage of being faster, and further were physical reasons why that would be a better way. But it was by no means clear at that point that one could implode a material and have the implosion go in nicely and smoothly so it all goes to one point rather than crumpling up in some complicated way, which would increase the critical mass, is the word you would say.

The beginning of the implosion program was a meeting at Los Alamos, which must have been in late March or early April. It was right in there, with Seth Neddermeyer, who joined the project from Caltech, who proposed the idea of implosion. As far as I know, nobody had thought about it, at least I had never heard of it up to that time. The gun method was the method. Neddermeyer proposed this idea. I was at that meeting and there was a lot of skepticism about it, whether it was practical at all. But Seth wanted to get on with the job and try it out.

Without any particular official recognition from the laboratory, he set out to do the early work on his own. He went to Bruceton, Pennsylvania, where the Bureau of Mines had an explosives research station, to learn something about explosions. I went with him. I was very interested in this thing. So we were there. Another thing I remember about that trip was meeting [George] Kistiakowsky. He was not in the project at that point, but he was connected with the Bruceton laboratory, and he came and met us there. I had known him before from Princeton. At the same time I knew Joe, I knew George Kistiakowsky. But he was there at Bruceton. Later, of course, he took over the program, but at that point it was just Seth, Seth and myself, really.

The first cylindrical implosions were done there. You take a piece of iron pipe and wrap explosives around it, and ignite at several points so they get a converging wave and squash these cylinders in. That was really the birth of the experimental work, long before experimental work on the gun method. That point is sometimes obscured in the histories. The work started earlier. That was a very interesting trip.

Then when he came back, he was able to get enough support to set up a little research station on what was called South Mesa, just south of the main technical center at Los Alamos, for doing implosion work. I assisted him on that. Explosives had to be something that could be made into odd shapes, so you want something that could be manipulated. The things we used then were powdered TNT and plastic explosives, the same thing that the terrorists like to use now. Looks just like putty, but you can mold it in any shape you want.

One experience there I remember, I will tell you, this little thing, I felt so stupid about it that I never told anybody about it until years later. I just felt as stupid as a person could get, but I will tell you now. I was carrying a box of powdered TNT in a wooden box about that big with quite a lot of the stuff in it, open top. At that time, I was a cigarette smoker. I walked through the woods and I suddenly realized, here was a cigarette bobbing up and down in my mouth with this big box of powdered TNT under it. [Laughs] I couldn’t release a hand, you know, to take the cigarette out of my mouth. Very carefully putting it down, very carefully removing the cigarette, and I never told anybody about that. Well, by now, one’s youthful stupidities don’t seem so important.

Those tests, of course, could not be very sophisticated, but they were all in cylindrical form, as I remember. Nothing as complicated as a sphere was done. It did show that you could take fairly thick-walled metal pipes and close them right in so that they became like solid bars, and that this was a practical method. Of course, you know from reading the histories that—and you probably heard from Kistiakowsky how the program went after that.

The other thing I will touch on is the gun program, which I became associated with later when Captain [William “Deak”] Parsons of the Navy was put into the project to take over the so-called gun program, and I became his deputy. I even shared an office with him for quite a while when we did not have space. The first task of the gun group was to set up a test stand, where experiments could be done. You have to have a gun emplacement and a gun and what they called a sand butt, which was nothing but a huge box full of sand that you fire projectiles into, so that you can find the pieces afterwards. Also, I guess, because there might be somebody else out there.

The Anchor Ranch was set up. It was probably over-designed, but everybody was very worried at that time about guns blowing up and so on. There were all kinds of horror stories about what happens when a gun blows up, which I guess is not a nice thing. Anchor Ranch was one of the old ranches, which was not part of the ranch school, but it was in the vicinity. The owner of the ranch had moved out and they had left everything behind. It was just a complete ranch house, barn, equipment, everything, including this nice flat area which would make a good test range, next to a canyon.

We built a control building down in the canyon down here, and the gun sits up there. After you get everything loaded, you go down here and get into your control room where it had big concrete walls, and fire the gun from there. You observe what has happened through a telescope, but more importantly, you go out afterwards and look at the pieces. See, at that point we were firing stuff that was really more complicated than it had to be, as we learned later, and I won’t go into the technical details of this. A lot of the work consisted of simply finding the pieces.

You fire the thing—it’s sort of interesting. In gunnery, they have something called a yaw card, which is just a piece of cardboard. You put that in front of a gun and when the projectile goes through, it goes so fast it cuts a hole just like the projection of the projectile, you see. If it was going sideways, it makes a rectangular hole. These were flat-nosed things we were firing. A round hole if it was going forward. If it was something complicated that breaks up, every piece makes its mark. So, we had one of those things and then we would have a crew of the local types who would get out their shovels and dig down in all this sand to find the pieces, and we would get them out and look at them.

My closing date—I just chose that rather arbitrarily, September 17, 1943—was when the first shot was fired at Anchor Ranch. Up to then it had just been preparation, planning and so on. From then on, it becomes late history.

I will close with one other little thing. In running a laboratory in a remote site, there are many things that you would have to do in a different way that you do ordinarily. For instance, power. Here if you want power, you just hook onto the local power company. I don’t know its name here. You got PG&E here? Do you get power from PG&E here? Probably not. Wherever you get it from, a guy comes and connects you to the line and you throw a switch.

No local power company [at Los Alamos], so some old diesel-run generators were acquired from an abandoned mine, I believe in Colorado, and were set up on the site. There were, as I remember, four of these things, and they were all hooked together and furnished power to the laboratory. It was run by one of these grizzled old-timers that had been doing this kind of thing—I think he came along with the generators, in fact. [Laughs]

It ran, but there were some interesting peculiarities. The two little stories that I’m going to tell: one of the things which you like to have for running sensitive equipment is stable frequency of voltage in a power supply. There were complaints about fluctuation. I had in my office two Esterline Angus recorders, one recording frequency and one recording voltage continuously. I would watch these things, and the frequency was wandering back and forth too much.

The power committee consisted of three people: John Williams, who was chairman, Bob Wilson, and myself. We went down to the power plant and conferred with this guy, and he said, “Well, we have a master clock. There are two hands. One hand is run by a pendulum clock and the other is run by a synchronous clock in your lines, and you are supposed to keep those hands going around together.” He said he always managed to keep the hands together. He said, “There are some little weights on the pendulum that I can change, and I will keep changing the weights and I keep those two hands together.”

The other frequency story: as the lab grew in size, the power plant became inadequate, so there was talk of running a line out from down south of there, where there existed a power supply. This man said, “That will never work.” He said, “You will lose so many cycles going up that hill, you’ll never be able to synchronize the [hands].”

I would now like to turn it over to Elsie for the personal side. [For Elsie McMillan’s lecture, please click here.]

Copyright 2016 Los Alamos National Laboratory. This transcript may not be quoted, reproduced, or redistributed in whole or in part by any means except with the written permission of the Los Alamos National Laboratory.