On a quiet afternoon in March 1958, a massive explosion ripped through the backyard of a family home in Mars Bluff, South Carolina. The source? A 7,600-pound nuclear bomb—dropped by the United States Air Force.
Yes, you read that right. The U.S. military accidentally released a nuclear bomb over American soil, and by sheer dumb luck, it didn’t detonate. But the conventional explosives inside still went off, obliterating a house, injuring six people, and leaving a massive crater where the backyard used to be.
How does something like this even happen? And more importantly, could it happen again?
The Day the Sky Dropped a Bomb
March 11, 1958, started like any other day for the Gregg family. Walter Gregg, a World War II veteran and former paratrooper, was outside working in his garage while his wife, Effie, was inside their small home.
A few feet away, his three children and a niece were playing near a tool shed in the backyard. Nothing seemed out of the ordinary.
Then, out of nowhere, the sky exploded.
A sudden, deafening blast threw the children into the air. The ground shook. Trees snapped like twigs. A massive cloud of smoke and debris engulfed the Gregg family’s house, tearing off the roof and shattering every window.
The Greggs were alive, but their home—and their entire backyard—was destroyed.
The explosion left a 70-foot-wide, 35-foot-deep crater right where their children had been playing. If they had been just a few steps closer, they would have been killed instantly.
How Do You ‘Accidentally’ Drop a Nuke?
The culprit was a B-47E-LM Stratojet bomber from Hunter Air Force Base in Georgia, part of the 375th Bombardment Squadron of the 308th Bombardment Wing. It had taken off at 4:34 p.m. and was en route to the United Kingdom, then North Africa, as part of Operation Snow Flurry, a Cold War-era mission designed to ensure bombers were ready for immediate action in case of war with the Soviet Union.
Onboard was a Mark 6 nuclear bomb. While the nuclear core was not installed, the bomb still contained about two tons of high explosives, designed to detonate in sequence to trigger a nuclear explosion under normal conditions.
About 25 minutes after takeoff, Captain Earl Koehler, the aircraft commander, noticed a fault light indicating that the bomb harness locking pin had not engaged. Concerned that the bomb might not be properly secured, he ordered Captain Bruce Kulka, the navigator and bombardier, to check the weapon.
Kulka entered the bomb bay and found that the bomb was hanging from a single shackle. He attempted to insert a steel pin through the shackle to prevent the weapon from falling in case of an electrical failure. Instead, he accidentally caused the bomb to unhook.
The 7,600-pound bomb fell onto the bomb bay doors, forcing them open and plummeting to the ground from an altitude of 15,000 feet.
Kulka nearly followed it. He managed to stop himself from falling out of the open bomb bay just in time.
Why Didn’t the Nuke Go Off?
A nuclear bomb doesn’t explode just because it hits the ground. The Mark 6 bomb required the nuclear capsule, which contained fissile material, to be inserted before it could cause a nuclear detonation. That capsule, stored in a separate container known as a “birdcage,” was still aboard the plane.
However, the bomb’s conventional explosives did go off.
The blast obliterated the Greggs’ garage and severely damaged their home. It also wrecked six other houses and a church in the area. Shrapnel from the explosion was found miles away.
The shockwave sent Walter Gregg flying inside his collapsing garage. His wife suffered a head injury from falling debris, while the Gregg children were hit by flying splinters and rubble. Their niece, the most seriously injured, required surgery for internal bleeding.
The family’s hens, kept in a nearby coop, were all killed instantly.
The Fallout (Not the Nuclear Kind)
Walter Gregg described the incident in an interview with The New York Times. He recalled that five seconds after the plane passed overhead, there was an explosion that “blew out the side and the top of the garage” just as his son ran inside with him. Timbers fell around them. The house, just 100 yards from the blast, had its roof blown in and one side completely torn apart.
After the explosion, another B-47 flew over Mars Bluff, photographing the impact site and documenting the damage. Within hours, military personnel cordoned off the area, retrieving debris and checking for radioactive contamination. The Air Force determined that any uranium tamper material from the bomb had not spread significantly, and cleanup crews from the Atomic Energy Commission and Los Alamos National Laboratory were dispatched to ensure the area was safe.
The military immediately launched an investigation. The crew of the B-47 was quietly transferred overseas. Despite the severity of the accident, no one was punished.
The Gregg family, left homeless and shaken, sued the Air Force. Five months later, they were awarded $54,000, the equivalent of over $580,000 today.
Mars Bluff Wasn’t the Only Close Call
While the Mars Bluff accident was the first widely reported case of a nuclear bomb being dropped on U.S. soil, it was far from the only one. In fact, it wasn’t even the worst.
Just a few weeks earlier, another B-47 had jettisoned a nuclear bomb off the coast of Georgia, and to this day, that bomb remains lost. The Mars Bluff incident was at least the 13th serious nuclear accident involving an American weapon at that point in history.
One of the closest calls came in 1961, when a B-52 bomber broke apart in mid-air over Goldsboro, North Carolina, dropping two nuclear bombs. One of those bombs nearly detonated—it had only a single safety switch preventing a nuclear explosion.
These incidents, known as “Broken Arrows,” are surprisingly common. The U.S. military has officially acknowledged at least 32 cases of lost, dropped, or accidentally detonated nuclear weapons. Some, like the one lost near Georgia, have never been recovered.
Could This Happen Again?
The military insists that today’s nuclear weapons are safer and that modern technology prevents accidents like Mars Bluff from happening again. After the incident, new security measures were put in place to prevent bombs from being accidentally jettisoned.
However, human error still exists. Mistakes happen, even with the most dangerous weapons on Earth. In recent decades, there have been close calls where nuclear weapons were accidentally transported without authorization or left unsecured.
The Mars Bluff accident serves as a chilling reminder of just how easily a simple mistake can lead to disaster.
The Bomb Crater Is Still There
Today, visitors to Mars Bluff can still see the crater left by the explosion. In 2008, the Florence City and County Historical Society placed a historical marker near the site, commemorating the day when a nuclear bomb fell out of the sky and nearly wiped out a family.
Walter Gregg and his family rebuilt their home and moved on with their lives. Despite nearly being killed by an Air Force blunder, Gregg maintained a sense of humor about the whole ordeal, once joking that he wished he could have at least kept the bomb as a souvenir.
But for the rest of us, it’s a sobering thought: nuclear bombs have fallen out of the sky before. And while Mars Bluff was lucky, the next mistake might not be so forgiving.
