The nuclear problem with Iran started 70 years ago in the desert of New Mexico. July 16, 1945, was a day with two dawns: the latter powered by hydrogen atoms fusing at a comfortable remove of 150 million kilometers. The earlier one entailed a blinding flash of white light fading away as the Trinity test of an atomic bomb exploded at 5:29 A.M. local time—“Up n' atom,” as the slogan for kids went from a little later in the new Atomic Age.

One dawn means a sky smeared with pink clouds drifting in a baby blue sky, accompanied by a chorus of birds singing in a wide flat valley carved by the Rio Grande and its tributaries. The other means a deafening roar that follows in the wake of a blinding flash and the world's first nuclear mushroom cloud.

The Trinity site within the White Sands Missile Range looks the same today as it does in color footage posted by the U.S. Department of Energy of preparations for the first plutonium bomb test. Tumbleweeds skip and hop across this dry and dusty land, the Russian imports piling up against barbed wire fences. A black-and-white film records the Trinity test, the explosion of a little gray sphere covered in wires, bolts and plugs atop a giant erector set reminiscent of an oil derrick. Scrawny geeks in white T-shirts with pencils behind their ears work in the innards of the Trinity bomb before it is raised carefully, ever so gingerly into position and left overnight.

Like the sacred site of some kind of new religion, the secretive missile range opens up to show Trinity twice a year, on a Saturday in spring and fall. So on another beautiful day in the high desert, I joined a procession of cars heading out into the scrubland and queuing up in a line that stretches for kilometers to pass through the Stallion Gate at the north end of the range that stretches for some 160 kilometers to the south through the region known as Jornada del Muerte, or Route of the Dead, a name given long before the nuclear test or the establishment of the missile range. Cattle graze placidly near the road while minivans wait at the turnoff, hawking "trinitite"—the new, greenish, flecked mineral produced by sand and dirt melted by the Trinity blast—for just $20 a pebble. Protesters hold up signs like "Speaking up for those silenced by the bombs" and "We are the Trinity downwinders."

After a short drive within the range, soldiers guide cars into a gravel parking lot next to a fence bearing signs that read in warning yellow "CAUTION: Radioactive Materials," accompanied by the now familiar jack-o’-lantern face that symbolizes radiation danger. The "Jumbo" bomb shield built to contain all the plutonium should a chain reaction fail sits outside the fenced entrance where vendors hawk day-glow green T-shirts reading "Duck and Cover," the same advice I got long ago in a cinderblock school hallway in St. Louis. An older man with a long, flowing gray beard dressed all in white wanders through the crowd blowing a shofar, perhaps to herald the apocalypse. Another young man with scraggly dirty blond hair wears a black T-shirt with Robert Oppenheimer's reflection on what he and his fellow scientists had wrought in the desert: "Now I am become Death, the destroyer of worlds" as the Hindu god Vishnu says in the Bhagavad Gita. People stop and stoop to paw through the dirt looking for trinitite—not just an illicit souvenir the federal government forbids one to remove but also a source rock for the newly proposed current geologic epoch known as the Anthropocene for our species’s world-changing ways. The wind sighs in the grass and rattles the inner fence that encircles the shallow depression of the blast site, marked by an obelisk of black stones with a plaque that reads "Trinity Site: Where the World's First Nuclear Device Was Exploded on July 16, 1945." A white replica of the “Fat Man” bomb dropped on Nagasaki on August 9, 1945, sits on a parked trailer next to the obelisk on the day I visit.

The bombs only got more destructive after Fat Man, including the so-called "Super," a hydrogen fusion weapon first tested in 1955 that kicked off the arms race between the U.S. and the Soviet Union that still has not ended, even if the U.S.S.R. has. In fact, the U.S. is in the process of refurbishing or replacing many of its aging warheads, like a newly modified W-80 bomb that will tip a new generation of ballistic missiles slated for the 2020s at an estimated cost of more than $10 billion. Explosive force started to be measured in megatons, like the hydrogen-bomb tipped Titan 2 intercontinental ballistic missiles arrayed around cities like Little Rock, Tucson and Wichita. A single one of these warheads could annihilate an entire metropolitan region on the other side of the planet.

For long decades now military men and women have sat behind three-ton blast doors more than 40 meters underground at the analog switches that could initiate the end of the world in less than a minute. The targets to be annihilated represented by punch codes in Mylar tape and a "No Lone Zone" policy in place to ensure that no person was ever left alone at the controls of apocalypse. Such nuclear missiles represent the apotheosis of efficient armed conflict—a total war finished in just a few hours thanks to mutual assured destruction. The launch message has yet to come, thankfully. Nuclear jobs are the most boring in the world until, all of a sudden and in an instant, they become the most existentially important and challenging in human history. "Another war with the weapons of mass destruction now available would destroy all existing political, economic and social systems, and set civilization back by a thousand years," as the then-U.N. Secretary General Trygve Lie put it in the pages of this magazine in 1950. "I do not believe there are many with such a suicidal bent of mind."

The U.S deployed all of this nuclear weapons know-how—especially the national labs and their mastery of "separative work units" needed to enrich fissile material—to craft a nuclear deal with Iran. The goal is to keep Iran from conducting its own Trinity test, as eight other nations have done in the years since 1945. Only one nation, South Africa, has ever forsworn such destructive secrets, although others like Argentina and Brazil have abandoned such research and former Soviet republics such as Ukraine have transferred weapons based on their soil to Russia. It remains to be seen what Iran will do.

The legacy of all this testing and bomb-building has scarred the landscape and people from Hanford in Washington State to Semipalatinsk in Kazakhstan to the dome-covered test site in the Marshall Islands. A global ear keeps track of earthquakes as well as the rumbles produced by nuclear tests in places like North Korea. Such tests are banned under a treaty that the U.S., among others, has yet to ratify, although this nation has not exploded a nuclear bomb in test since 1992 and not built a new kind of nuclear weapon since 1991. Decommissioned Russian weapons have even been reprocessed and used as fuel in U.S. nuclear power plants, a program that ended in 2013 known as Megatons to Megawatts.

Still, thousands of such bombs remain in the U.S. and Russian arsenals and the nuclear threat remains all too real. As it stands, the U.S. admits to less than 2,000 warheads atop missiles, onboard submarines and ready to be loaded onto long-range bombers, like the Fat Man and Little Boy dropped on Japan in 1945 in the wake of the Trinity test. Nine nations—China, France, India, Israel, North Korea, Pakistan, Russia, the U.S. and the U.K.—now stand poised to do the same to their adversaries.

Like the Trinity downwinders, something of that first test and the more than 1,000 U.S. tests that followed remains in us all. It's in my teeth, my wife's teeth, my kids' teeth, your teeth and bones—the rise and fall of nuclear testing marked in dental records, known as the bomb curve, a fading residue of radioactive isotopes. Civilization remains on that route, no matter how much some choose to forget. As the old missile wing saying goes: "Peace is never fully won. It is only kept moment to moment."