The Trinity Test Site, in New Mexico, where the first atomic bomb was tested, is inside one of the most secret areas in the United States, the White Sands Missile Range. Normally the entire area is off-limits and under strict security. But on just two days each year the Trinity Site is open to the public.

Me, at the Trinity Site

When I was planning my loop around the West, a Trinity visit wasn’t even on my mind. I knew that it was only open sporadically but I didn’t know when. It wasn’t until I was at the National Nuclear Testing Museum in Las Vegas that I thought of it, and asked one of the Museum staff if they knew when the Trinity Site would next be open. They told me it was the first Saturday in April and the first Saturday in October, which would be October 1. About three and a half weeks away.

So I changed my plans to take advantage of the opportunity. I had originally intended to go from Vegas to Arizona, stopping in Winslow, Phoenix and Tucson before looping up through New Mexico to Albuquerque and then on to Texas for the winter. But now, instead, I would go from Vegas straight to New Mexico, staying in Alamogordo long enough to take the side trip to Trinity.

When I arrived in Alamogordo, the first place I visited was the Space History Museum, and asked the staff there if they knew of any shuttle buses that would be going out to the Trinity Site. Well, as it happened, the Museum itself was taking a bus there, and it was almost full. So I paid my money and reserved a spot. And on the appointed day I got myself up at 6am and met the shuttle bus in the Museum’s parking lot. (With my jacket on–you would think deserts are always hot, but it actually gets pretty cold there when the sun is down.)

Our bus was part of a local caravan, made up of other buses and about 70 private vehicles from the area, which assembled at a local high school parking lot. There were other caravans from Albuquerque and Texas as well, and apparently these are the only way to get into the site. We would have an escort of Military Police from the Missile Range with us the entire time, and before the caravan pulled out, security personnel from White Sands examined ID from everyone. We were given a lecture about the rules we were to follow: no photography anywhere on the base except for the actual Trinity locations. Stay with the group–security personnel are authorized to use deadly force against intruders. Any sort of anti-war or anti-nuclear protest actions or speeches at the site would be dealt with immediately. Don’t pick up any metal objects if you see them–there’s occasional unexploded ordinance scattered around the range. And we were not to take anything away from the site–particularly pieces of “trinitite”, the melted sand-glass produced by the explosion. As a National Historic Landmark, it is illegal to remove or collect anything. We were also reassured about the radiation. Because the Trinity device was not very big (by today’s standards) and was detonated off the ground, it did not actually produce much fallout, and nearly all of the radiation from the explosion is now gone. A typical two-hour visit to Ground Zero exposes us to about one millirem of radiation–about one-sixth the amount one would receive from a medical chest x-ray. So the effects are negligible, and we won’t be glowing in the dark.

Once we were given the ground rules, the group set off–a parade of vehicles probably a mile long, led by local police and military security.

Our caravan had a bit of an adventure. In the desert, temperature inversions are pretty common, and they often cause local fog banks. We happened to hit one of these not long after we entered the Missile Range. Apparently in the fog, somebody in the middle of the caravan couldn’t see the car in front of them and missed a turn, and merrily led the rest of the group down a road we were not supposed to be on. The military security folks showed up pretty quickly and turned everyone back around.

Most history books have the Trinity Test as happening “near Alamogordo”. But in the West, “near” is a relatively loose term. The site is actually 100 miles from the town, and it took us almost two hours to get there. Along the way, we were given a history lesson by a professor from New Mexico State University, who described the discovery of nuclear fission in Germany, the fear that the Nazis might develop an atomic bomb, the Manhattan Project to beat the Germans to it, the work at Los Alamos, and the design and testing of the implosion bomb at Trinity.

In 1940, when it looked as though the Nazis could be invading England any day now, the US and UK reached an agreement to train British pilots in the United States. A bombing range was set up near Alamogordo, which later became the White Sands Missile Range.

By December 1944, the Manhattan Project was certain that the uranium Little Boy bomb would work, so no testing was planned for it–the prototype itself would be dropped on Japan. But the plutonium implosion Fat Man design was much more complex, and it was decided to test-detonate it. A test site was selected in the northeast part of the bombing range, which was codenamed “Trinity”.

The implosion bomb worked by detonating a complex layer of explosives around a small plutonium core, which squeezed the core until it triggered a nuclear explosion. But if the plutonium core failed to detonate, the 2.5 tons of conventional explosive would still blow it apart. Since the plutonium had taken a tremendous effort to produce (and also since scattered plutonium dust was a lethal health risk), the scientists at Los Alamos decided to place the test bomb (known as “The Gadget”) inside a specially-manufactured 214-ton steel jar, which they called “Jumbo”, to contain the plutonium in the event of a fizzle. As it turned out, the physicists later decided that Jumbo wasn’t necessary, and left the huge metal jug sitting near the test tower.

On June 12, the Manhattan Project team began assembling the Gadget, working at the MacDonald ranch house two miles away from Ground Zero. Once the plutonium core was ready, it was taken by truck to the test site, where it was inserted into the explosives blanket and all the detonators and timers were connected. On July 13, the work was finished, and the next morning the completed bomb was hoisted to the top of the 100-foot steel tower.

The test was scheduled for 4am on July 16, but a thunderstorm delayed things. Finally the weather cleared, and at 5:29am on July 16, 1945, the detonators were triggered. The blast was the equivalent of 19,000 tons of TNT. The shock wave broke windows up to 120 miles away, and woke people from their beds in Alamogordo and Albuquerque. The 100-foot test tower was completely vaporized, with only fragments of the concrete foundations remaining. Because the bomb had exploded in the air, it did not make a crater, but instead pressed a shallow bowl-like depression underneath it, lined with glassy melted sand that became known as “trinitite”.

The Army sent out a press release explaining that there had been an accidental explosion at an ammo dump. The atomic test was not revealed publicly until after the bombs had been dropped on Hiroshima and Nagasaki.

In the immediate aftermath, the Trinity site was surrounded by a fence and was offlimits to the public. In 1952 the Atomic Energy Commission decided to remove nearly all of the trinitite to make the area safer for visitors (one small portion of the original crater was covered by a sheet-metal building which is still there, but the glass layer has now become covered with dust and sand). In 1953 an “open house” was held in which about 650 civilians were allowed in to Ground Zero, and sporadic visits were allowed over the next few years. In 1967 and 1972 new security fences were added. Today, the Trinity site is open to the public two days a year, and visitors are able to walk out to Ground Zero and ride shuttle buses to see the MacDonald ranch where the bomb core was assembled.

Here are some photos from a visit to Trinity.

Assembling the caravan

Checking IDs

The bus arrives at the site

The MacDonald ranch where the nuclear core was assembled

Inside the “Plutonium Room”

Jumbo actually survived the trinity explosion, but was blown apart later by the Army ion an explosives test

Walking towards Ground Zero

They aren’t kidding about the security

They REALLY aren’t kidding….

What’s left of the 100-foot steel tower that held the bomb

A Fat Man bomb casing on display

The plaque at Ground Zero

Bits of Trinitite on display