Trinity Site History

Trinity Site is where the first atomic bomb was tested at 5:29:45 a.m. Mountain War Time on July 16, 1945. The 19-kiloton explosion not only led to a quick end to the war in the Pacific but also ushered the world into the atomic age. All life on Earth has been touched by the event which took place here.

The 51,500-acre area was declared a national historic landmark in 1975. The landmark includes base camp, where the scientists and support group lived, ground zero, where the bomb was placed for the explosion, and the McDonald ranch house, where the plutonium core to the bomb was assembled. Visitors to a Trinity Site Open House see ground zero and the McDonald ranch house. In addition, one of the old instrumentation bunkers is visible beside the road just west of ground zero.

The Manhattan Project

The story of Trinity Site begins with the formation of the Manhattan Project in June 1942. The project was given overall responsibility for designing and building an atomic bomb. At the time it was a race to beat the Germans who, according to intelligence reports, were building their own atomic bomb.mdasf.gif

Under the Manhattan Project three large facilities were constructed. At Oak Ridge, Tenn., huge gas diffusion and electromagnetic process plants were built to separate uranium 235 from its more common form, uranium 238. Hanford, Wash. became the home for nuclear reactors which produced a new element called plutonium. Both uranium 235 and plutonium are fissionable and can be used to produce an atomic explosion.

Los Alamos was established in northern New Mexico to design and build the bomb. At Los Alamos many of the greatest scientific minds of the day labored over the theory and actual construction of the device. The group was led by Dr. J. Robert Oppenheimer who is credited with being the driving force behind building a workable bomb by the end of the war.

Two Bomb Designs

Los Alamos scientists devised two designs for an atomic bomb, one using uranium 235 and another using plutonium. The uranium bomb was a simple design and scientists were confident it would work without testing. The plutonium bomb was more complex and worked by compressing the plutonium into a critical mass which sustains a chain reaction. The compression of the plutonium ball was to be accomplished by surrounding it with lense-shaped charges of conventional explosives. They were designed to all explode at the same instant. The force is directed inward, thus smashing the plutonium from all sides.

In an atomic explosion, a chain reaction picks up speed as atoms split, releasing neutrons plus great amounts of energy. The escaping neutrons strike and split more atoms, thus releasing still more neutrons and energy. In a nuclear explosion this all occurs in a millionth of a second with billions of atoms being split.

Project leaders decided a test of the plutonium bomb was essential before it could be used as a weapon of war. From a list of eight sites in California,Texas, New Mexico and Colorado, Trinity Site was chosen as the test site. The area already was controlled by the government because it was part of the Alamogordo Bombing and Gunnery Range which was established in 1942. The secluded Jornada del Muerto was perfect as it provided isolation for secrecy and safety, but was still close to Los Alamos.

Beginnings of Trinity Site

In the fall of 1944 soldiers starting arriving at Trinity Site to prepare for the test. Marvin Davis and his military police unit arrived from Los Alamos at the site on Dec. 30, 1944. The unit set up security checkpoints around the area and had plans to use horses to ride patrol. According to Davis the distances were too great and they resorted to jeeps and trucks for transportation. The horses were sometimes used for polo, however. Davis said that Capt. Bush, basecamp commander, somehow got the soldiers real polo equipment to play with but they preferred brooms and a soccer ball.

Other recreation at the site included volleyball and hunting. Davis said Capt. Bush allowed the soldiers with experience to use the Army rifles to hunt deer and pronghorn. The meat was then cooked up in the mess hall. Leftovers went into soups which Davis said were excellent.

Photos: Crawdad and ScorpionOf course, some of the soldiers were from cities and unfamiliar with being outdoors a lot. Davis said he went to relieve a guard at the Mockingbird Gap post and the soldier told Davis he was surprised by the number of "crawdads" in the area considering it was so dry. Davis gave the young man a quick lesson on scorpions and warned him not to touch.

Throughout 1945 other personnel arrived at Trinity Site to help prepare for the test. Carl Rudder was inducted into the Army on Jan. 26, 1945. He said he passed through four camps, took basic for two days and arrived at Trinity Site on Feb. 17. On arriving he was put in charge of what he called the "East Jesus and Socorro Light and Water Company." It was a one-man operation, himself. He was responsible for maintaining generators, wells, pumps and doing the power line work.

A friend of Rudde, Loren Bourg, had a similar experience. He was a fireman in civilian life and ended up trained as a fireman for the Army. He worked as the station sergeant at Los Alamos before being sent to Trinity Site in April 1945. In a letter Bourg said, "I was sent down here to take over the fire prevention and fire department. Upon arrival I found I was the fire department, period."

As the soldiers at Trinity Site settled in they became familiar with Socorro. They tried to use the water out of the ranch wells but found it so alkaline they couldn't drink it. In fact, they used Navy salt-water soap for bathing. They hauled drinking water from the fire house in Socorro. Gasoline and diesel was purchased from the Standard bulk plant in Socorro.

According to Davis, they established a post office box, number 632, in Socorro so getting their mail was convenient. All the trips into town also offered them the chance to get their hair cut in the barbershop in town. If they didn't use the shop, SGT Greyshock used horse clippers to trim their hair.


The bomb design to be used at Trinity Site actually involved two explosions. First there would be a conventional explosion involving the TNT and then, a fraction of a second later, the nuclear explosion, if a chain reaction was maintained. The scientists were sure the TNT would explode, but were initially unsure of the plutonium. If the chain reaction failed to occur, the TNT would blow the very rare and dangerous plutonium all over the countryside.

Photo: JumboBecause of this possibility, Jumbo was designed and built in Ohio. Originally it was 25 feet long, 10 feet in diameter and weighed 214 tons. Scientists were planning to put the bomb in this huge steel jug because it could contain the TNT explosion if the chain reaction failed to materialize. This would prevent the plutonium from being lost. If the explosion occurred as planned, Jumbo would be vaporized.

Jumbo was brought to Pope, N.M., by rail and unloaded. A specially-built trailer with 64 wheels was used to move Jumbo the 25 miles to Trinity Site.

As confidence in the plutonium bomb design grew it was decided not to use Jumbo. Instead, it was placed under a steel tower about 800 yards from ground zero. The blast destroyed the tower, but Jumbo survived intact.

Today it rests at the entrance to ground zero so all can see it. The ends are missing because, in 1946, the Army placed eight 500-pound bombs inside it and detonated them.

100-Ton Test on May 7

To calibrate the instruments which would be measuring the atomic explosion and to practice a countdown, the Manhattan scientists ran a simulated blast on May 7. They stacked 100 tons of TNT onto a 20-foot wooden platform just southeast of ground zero. Louis Hempelmann Inserted a small amount of radioactive material from Hanford into tubes running through the stack of crates. The scientists hoped to get a feel for how the radiation might spread in the real test by analyzing this test. The explosion destroyed the platform, leaving a small crater with trace amounts of radiation in it.

On July 12 the two hemispheres of plutonium were carried to the George McDonald ranch house just two miles from ground zero. At the house, Brig. Gen. Thomas Farrell, deputy to Maj. Gen. Leslie Groves, was asked to sign a receipt for the plutonium. Farrell later said, "I recall that I asked them if I was going to sign for it shouldn't I take it and handle it. So I took this heavy ball in my hand and I felt it growing warm, I got a certain sense of its hidden power. It wasn't a cold piece of metal, but it was really a piece of metal that seemed to be working inside. Then maybe for the first time I began to believe some of the fantastic tales the scientists had told about this nuclear power."

At the McDonald ranch house the master bedroom had been turned into a clean room for the assembly of the bomb core. According to Robert Bacher, a member of the assembly team, they tried to use only tools and materials from a special kit. Several of these kits existed and some were already on their way to Tinian by different routes. The idea was to test the procedures and tools at Trinity as well as the bomb itself.

At one minute past midnight on Friday, July 13, the explosives assembly left Los Alamos for Trinity Site. Later in the morning, assembly of the plutonium core began. According to Raemer Schreiber, Robert Bacher was the advisor, Marshall Holloway and Philip Morrison had overall responsibility. Louis Slotin, Boyce McDaniel and Cyril Smith were responsible for the mechanical assembly in the ranch house. Later Holloway was responsible for the mechanical assembly at the tower.

In the afternoon of the 13th the core was taken to ground zero for Insertion into the bomb mechanism.

The bomb was assembled under the tower on July 13. The plutonium core was Inserted into the device with some difficulty. On the first try it stuck. After letting the temperatures of the plutonium and casing equalize the core slid smoothly into place. Once the assembly was complete many of the men went swimming in the water tank east of the McDonald ranch house.

The next morning the entire bomb was raised to the top of the 100-foot steel tower and placed in a small shelter. A crew then attached all the detonators and by 5 p.m. it was complete.

Observation Points

Photo: Gen. Leslie Groves and Dr. Robert OppenheimerThree observation points were established at 10,000 yards from ground zero.These were wooden shelters protected by concrete and earth. The south bunker served as the control center for the test. The automatic firing device was triggered from there as key men such as Dr. Robert Oppenheimer, head of Los Alamos, watched. None of the manned bunkers are left.

Many scientists and support personnel, including Gen. Leslie Groves, head of the Manhattan Project, watched the explosion from base camp which was ten miles southwest of ground zero. All the buildings at base camp were removed after the test. Most visiting VIPs watched from Compania Hill, 20 miles northwest of ground zero.

The test was scheduled for 4 a.m. July 16, but rain and lightning early that morning caused it to be postponed. The device could not be exploded under rainy conditions because rain and winds would increase the danger from radioactive fallout and interfere with observation of the test. At 4:45 a.m. the crucial weather report came through announcing calm to light winds with broken clouds for the following two hours.

At 5:10 the countdown started and at 5:29:45 the device exploded successfully. To most observers the brilliance of the light from the explosion, watched through dark glasses, overshadowed the shock wave and sound that arrived later.

What It Was Like

Hans Bethe, one of the contributing scientists, wrote "it looked like a giant magnesium flare which kept on for what seemed a whole minute but was actually one or two seconds.The white ball grew and after a few seconds became clouded with dust whipped up by the explosion from the ground and rose and left behind a black trail of dust particles."

Joe McKibben, another scientist, said, "We had a lot of flood lights on for taking movies of the control panel. When the bomb went off, the lights were drowned out by the big light coming in through the open door in the back."

Others were impressed by the heat they immediately felt. Military policeman Davis said, "The heat was like opening up an oven door, even at 10 miles." Dr. Phillip Morrison said, "Suddenly, not only was there a bright light but where we were, 10 miles away, there was the heat of the sun on our faces ..... Then, only minutes later, the real sun rose and again you felt the same heat to the face from the sunrise. So we saw two sunrises."

Although no information on the test was released until after the atomic bomb was used as a weapon against Japan, people in New Mexico knew something had happened. The shock broke windows 120 miles away and was felt by many at least 160 miles away. Army officials simply stated that a munitions storage area had accidently exploded at the Alamogordo Bombing Range.

The explosion did not make much of a crater. Most eyewitnesses describe the area as more of a small depression instead of a crater. The heat of the blast vaporized the steel tower and melted the desert sand and turned it into a green glassy substance. It was called Trinitite and can still be seen in the area. At one time Trinitite completely covered the depression made by the explosion. Afterwards the depression was filled and much of the Trinitite was taken away by the Nuclear Energy Commission.

To the west of the monument is a low structure which is protecting an original portion of the crater area. Trinitite is visible through openings in the roof.

The McDonald Ranch House

The George McDonald ranch house sits within an 85`x85` low stone wall. The house was built in 1913 by Franz Schmidt, a German immigrant, and an addition was constructed on the north side in the 1930`s by the McDonalds. There is a display on the Schmidt family in the house during each open house.

McDonald ranch houseThe ranch house is a one-story, 1,750 square-foot building. It is built of adobe which was plastered and painted. An ice house is located on the west side along with an underground cistern which stored rain water running off the roof. At one time the north addition contained a toilet and bathtub which drained into a septic tank northwest of the house.

There is a large, divided water storage tank and a Chicago Aeromotor windmill east of the house. The scientists and support people used the north tank as a swimming pool during the long hot summer of 1945. South of the windmill are the remains of a bunkhouse and a barn which was part garage. Further to the east are corrals and holding pens. The buildings and fixtures east of the house have been stabilized to prevent further deterioration.

The ranch was abandoned in 1942 when the Alamogordo Bombing and Gunnery Range took over the land to use in training World War II bombing crews. The house stood empty until the Manhattan Project support personnel arrived in early 1945.

Inside the house the northeast room (the master bedroom) was designated the assembly room. Workbenches and tables were installed. To keep dust and sand out of instruments and tools, the windows were covered with plastic. Tape was used to fasten the edges of the plastic and to seal doors and cracks in the walls.

The explosion, only two miles away, did not significantly damage the house. Most of the windows were blown out, but the main structure was intact. Years of rain water dripping through holes in the roof did much more damage. The barn did not do as well. During the Trinity test the roof was bowed inward and some of the roofing was blown away. The roof has since collapsed.

The house stood empty and deteriorating until 1982 when the U.S. Army stabilized the house to prevent any further damage. Shortly after, the Department of Energy and U.S. Army provided the funds for the National Park Service to completely restore the house. The work was done in 1984. All efforts were directed at making the house appear as it did on July 12, 1945.

A Quick End to the War

The story of what happened at Trinity Site did not come to light until after the second atomic bomb was exploded over Hiroshima, Japan, on August 6. President Truman made the announcement that day. Three days later, August 9, the third atomic bomb devastated the city of Nagasaki, and on August 14 the Japanese surrendered.

Trinity Site became part of what was then White Sands Proving Ground. The proving ground was established on July 9, 1945, as a test facility to investigate the new rocket technology emerging from World War II. The land, including Trinity Site and the old Alamogordo Bombing Range, came under the control of the new rocket and missile testing facility.

Interest in Trinity Site was immediate. In September press tours to the site started. One of the famous photos of ground zero shows Robert Oppenheimer and General Leslie Groves surrounded by a small group of reporters as they examine one of the footings to the 100-foot tower on which the bomb was placed. That picture was taken Sept. 11. The exposed footing is still visible at ground zero. On Sept. 15-17 George Cremeens, a young radio reporter from KRNT in Des Moines, visited the site with soundman Frank Lagouri. They flew over the crater and interviewed Dr. Kenneth Bainbridge, Trinity test director, Capt. Howard Bush, base camp commander.

Back in Iowa, Cremeens created four 15-minutes reports on his visit which aired Sept. 24, 26, 27 and 29. A 15-minute composite was made and aired on the ABC Radio Network. For his work Cremeens received a local Peabody Award for "Outstanding Reporting and Interpretation of the News."

At first Trinity Site was encircled with a fence and radiation warning signs were posted. The site remained off limits to military and civilian personnel of the proving ground and closed to the public.

The First Visits

Logo: Atomic Energy CommissionIn 1952 the Atomic Energy Commission let a contract to clean up the site. Much of the Trinitite was scraped up and buried. In September 1953 about 650 people attended the first Trinity Site open house. A few years later a small group from Tularosa visited the site on an anniversary of the explosion to conduct a religious service and prayers for peace. Similar visits have been made annually in recent years on the first Saturday in October.

In 1967 the inner oblong fence was added. In 1972 the corridor barbed wire fence which connects the outer fence to the inner one was completed. Jumbo was moved to the parking lot in 1979.

Visits to the site are now made in April and October because it is generally so hot in July on the Jornada del Muerto.

White Sands Missile Range

White Sands Missile Range has developed from a simple desert testing site for the V-2 into one of the most sophisticated test facilities in the world. The mission of White Sands Missile Range begins with a customer, a service developer, or another federal agency, which is ready to find out if engineers and scientists have built something which will perform according to job specifications. It ends when an exhaustive series of tests has been completed and a data report has been delivered to the customer.

Between the beginning and the end of the test program, be it the Army Tactical Missile System or newly designed automobiles, range employees are involved in every operation connected with the customer and his product. The range can and does provide everything from rat traps to telephones, from equipment hoists and flight safety to microsecond timing.

We shake, rattle and roll the product, roast it, freeze it, subject it to nuclear radiation, dip it in salt water and roll it in the mud. We test its paint, bend its frame and find out what effect its propulsion material has on flora and fauna.

In the end, if it`s a missile, we fire it, record its performance and bring back the pieces for post mortem examination. All test data is reduced and the customer receives a full report.

For more information on Trinity Site or White Sands Missile Range contact the range's Public Affairs Office.


Historic Sources

Einstein's Letter:

This is the text of the letter signed by Albert Einstein which was delivered to President Franklin Roosevelt by Alexander Sachs on October 11, 1939. The chief author is believed to be Leo Szilard.

Albert Einstein
Old Grove Rd.
Nassau Point
Peconic, Long Island
August 2d, 1939

F.D. Roosevelt
President of the United States
White House
Washington, D.C.

Some recent work by E. Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future. Certain aspects of the situation which has arisen seem to call for watchfulness and, if necessary, quick action on the part of the Administration. I believe therefore that it is my duty to bring to your attention the following facts and recommendations.

In the course of the last four months it has been made probable--through the work of Joliot in France as well as Fermi and Szilard in America--that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium-like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future.

This new phenomenon would also lead to the construction of bombs, and it is conceivable--though much less certain--that extremely powerful bombs of a new type may thus be constructed. A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air.

The United States has only very poor ores of uranium in moderate quantities. There is good ore in Canada and the former Czechoslovakia, while the most important source of uranium is the Belgian Congo.

In view of this situation you may think it desirable to have some permanent contact maintained between the Administration and the group of physicists working on chain reactions in America. One possible way of achieving this might be for you to entrust with this task a person who has your confidence who could perhaps serve in an unofficial capacity. His task might comprise the following:

a) to approach Government Departments, keep them informed of the further development, and put forward recommendations for Government action, giving particular attention to the problems of securing a supply of uranium ore for the United States.

b) to speed up the experimental work, which is at present being carried on within the limits of the budgets of University laboratories, by providing funds, if such funds be required, through his contacts with private persons who are willing to make contributions for this cause, and perhaps also by obtaining the co-operation of industrial laboratories which have the necessary equipment.

I understand that Germany has actually stopped the sale of uranium from the Czechoslovakian mines which she has taken over. That she should have taken such early action might perhaps be understood on the ground that the son of the German Under-Secretary of State, von Weizaecker, is attached to the Kaiser-Wilhelm-Institut in Berlin where some of the American work on uranium is now being repeated.


Yours very truly
(signed) A. Einstein


SOURCE: U.S. Army in World War II Special Studies Manhattan: The Army and the Atomic Bomb
by Vincent C. Jones
Center of Military History
United States Army


Evacuation Report:

This is a report filed by Major Palmer on July 18, 1945. It deals with the plans to evacuate civilians around the Trinity Site area if high concentrations of radioactive fallout drifted off the Alamogordo Bombing Range.

Evacuation Detachment at Trinity

Detachment, Equipment, Personnel, Organization, Base Operations.

A. Equipment and Personnel.

This detachment consisted of 140 enlisted men, 4 officers, 140 vehicles, including one 500 gallon improvised water tank for drinking purposes, 2 lister bags, latrine flies, 30 pyramidal tents, 1000 type "C" and "K" rations, coffee, sugar, milk, and three field ranges.

B. Organization.

The detachment was formed into four platoons of nine vehicles each. The first and second platoons made up the first section under the Command of Captain Huene. The third and fourth platoons made up the second section under the Command of First Lieutenant M. Miller. Each vehicle had a driver and two men; three jeeps, under the direct supervision of the detachment Commander to act as messengers; one two-way radio vehicle.

C. Operating Base.

The detachment moved into its bivouac area 14 July. For security reasons this area was 4O miles from Trinity; the detachment remained there until the morning of 15 July, then moved to a semi-permanent Base Camp, with an alternate base site Selected. The Base Camp was set-up as a company; latrine dry flies put up; lister bags hung, and field ranges set up. The rest of the day and night was spent in briefing the men and having the section leaders and drivers familiarize themselves with the roads and dwellings in their assigned sections, and visiting Trinity headquarters for instructions. The Base Camp was approximately nine miles from Zero. The detachment Commander returned to Base Camp from Trinity around Mid night 15 July with last minute instructions. Major Miller was assigned the radio vehicle and put in Command of the Base Camp. The detachment was alerted in case the wind shifted in that direction, so it could move quickly to the alternate site.

D. Operations.

The orders received by the detachment Commander from General Farrell were generally as follows:

1. The two prepared press releases were made known to the detachment Commander. One in case of no evacuation, which stated briefly that an ammunition dump had blown up; and one in case of evacuation, which stated that an ammunition dump had blown up which contained gas shells and the people would be evacuated for 24 hours to protect them from the gas.

2. The detachment Commander would work with Mr. Hoffman and Mr. Herschfelter, with their crew of monitors, and was to evacuate upon Mr. Hoffman´s request.

The detachment Commander planned, in case of evacuation, to set-up the Base Camp as a shelter for the people; tents and shelters would be provided to cover and feed 450 people for two days. This was ample shelter for the small population centers that were close enough to be in immediate danger. The larger centers were some distance away and there was ample time to transport them to Alamogordo Air Field and house them in barracks. In cases of one or two families, it was planned to send them to a hotel in a near-by town.

The area in the vicinity of the shot was divided into sections and each section leader was responsible for his section, with additional help if needed.

A jeep was assigned to Trinity headquarters, Major Miller at Base Camp, and to the detachment Commander during the operation, to supplement radio communications.

Immediately after the shot, the wind drift was ascertained to be sure the Base Camp was not in danger. Monitors were immediately sent out in the direction of the cloud drift to check the approximate width and degree of contamination of the area under the cloud. A small headquarters was set-up at Bingham, near the center of the area in the most immediate danger. The monitors worked in a wide area from this base reporting in to Mr. Hoffman or Mr. Herschfelter. One re-enforced platoon, under Captain Huene, was held at Bingham; the rest of the detachment was held in reserve at Base Camp. Fortunately no evacuations had to be made.

Mr. Hoffman released the detachment about 1300 hours 16 July; by that time, any danger of serious contamination had passed.

The detachment Commander would like to take this time to say that the Officers and men of the detachment were alert, obedient, and conducted themselves in a superior manner throughout the experiment.

Major, C.E.
Detachment Commander


Eyewitness Account:


((Smith watched from Compania Hill near present-day Stallion Range Center))


DATE: 5 September 1945

TO: File

FROM: Ralph Carlisle Smith

SUBJECT: Comments on Trinity Test Shot Trip.

At about 1945 MWT, 15 July 1945, the coordinating council started from the Los Alamos Technical Area, riding in a three bus convoy with three G.I. sedans driven by Convoy Commander Captain George Turner, Mr. David Dow, and Dr. Earl Long and with a G.I. truck carrying spare equipment. The first stop was at the Camel on the Santa Fe Road. Then through back roads of Santa Fe to outskirts of Albuquerque where we stopped twenty minutes for convoy to be reassembled. The truck had broken down and the sedans stopped to get passengers at Santa Fe (Dr. C.A. Thomas).

We then proceeded to Wilson´s garage to get gas, remaining in Albuquerque for about 45 minutes -- the passengers wandering about town. At the Hilton, Sir James Chadwick, William Laurence, William Fouler, Tom Lauritsen, Charles Lauritsen, Major Ackerman, and an Army Captain (S-2) awaited to convoy. 2nd Lt. Dazzo (S-2) was there but was returning to Los Alamos.

We proceeded to Trinity (just beyond San Antonio, N. Mex) on Route U.S. 385 at a turn off marked Harriets Ranch. We were first stopped at the bivouac of Major T.O. Palmer´s Special Detachment of Engineers, who were stationed there for any emergency such as evacuation of personnel. After a brief check we proceeded to the Military Police Post No. 2 which was about 20 miles from zero point and about ten miles from the Trinity Base Camp. This was approximately 0200 to 0230 16 July 1945. About 0500 the searchlights allegedly at 6 miles from zero point started playing about, apparently fixing cloud elevation. At about 0520, the warning came by radio that the test was about to take place in 10 minutes. 1st Lt. Schaeffer, a civilian, and I stretched out on a blanket facing south to the spot where the several searchlights seemed to be focusing on the ground. A glow was appearing in the sky toward the East so that the mountain range stood out quite distinctly. The road was to our right and the buses to the rear of us. It was bright enough that you could identify people several hundred feet away. 1st Lt. Huene fired a rocket at minus six minutes and again at minus three. The latter did not explode in the air, hence another rocket went up about minus one minute. About then you could hear the warning siren at the bivouac area. I was staring straight ahead with my open left eye covered by a welders glass and my right eye remaining open and uncovered. Suddenly, my right eye was blinded by a light which appeared instantaneously all about without any build up of intensity. My left eye could see the ball of fire start up like a tremendous bubble or nob-like mushroom. I Dropped the glass from my left eye almost immediately and watched the light climb upward. The light intensity fell rapidly hence did not blind my left eye but it was still amazingly bright. It turned yellow, then red, and then beautiful purple. At first it had a translucent character but shortly turned to a tinted or colored white smoke appearance. The ball of fire seemed to rise in something of toadstool effect. Later the column proceeded as a cylinder of white smoke; it seemed to move ponderously. A hole was punched through the clouds but two fog rings appeared well above the white smoke column. There was a spontaneous cheer from the observers. Dr. von Neumann said "that was at least 5,000 tons and probably a lot more." My estimate of the width of the ball of fire was guessed to be 1 to 2 miles at that time. Someone said keep your mouth open and just then, about 1 1/2 to 2 minutes after the light flash, a sharp loud crack swept over us -- it reverberated through the mountain like thunder. Several small flashes took place some distance from and after the big flash, apparently part of a measuring system. Commander Bradbury said that the cloud was up over 20,000 feet and still rising. The top of the cloud was moving slightly northeast and was being sheared off. At about 0555, we were aboard the buses and started home again. We stopped for relief on the road between Albuquerque and Santa Fe, we gassed at Santa Fe (Closson and Closson) but did not dismount. We arrived at the Hill at about 1300 16 July 1945.

Signed by Ralph Carlisle Smith

((Ralph Smith was a lawyer at Los Alamos))