" " Yes, an actual atomic bomb was dropped on South Carolina in the 1950s. What's the history behind this obscure incident? Bettmann/Good Studio/Getty Images

In January 1953, the Gregg family moved into a stoutly constructed home in a rural part of eastern South Carolina, on land that had been in their family for 100 years. They had no idea that five years later, they would earn the dubious honor of being the first and only family to survive the first and only atomic bomb dropped on American soil — by Americans.

On March 11, 1958, two of the Greggs' children — Helen, 6, and Frances, 9 — entertained their 9-year-old cousin Ella Davies. The girls were horsing around in a playhouse adjacent to the family's garden while nearby, the Gregg girls' father, Walter, and brother, Walter Jr., worked in a toolshed.

By midafternoon, the sisters and their cousin had wandered about 200 feet (60 meters) away from the playhouse and were playing in the yard beside their home. Inside, their mother sat sewing in the front parlor.

Then, at 4:19 p.m., a member of the crew aboard a U.S. Air Force B-47E bomber accidentally released a nuclear weapon that landed on the girls' playhouse and the family's nearby garden, creating a massive crater with a circumference of 50 feet (15 meters) and depth of 35 feet (10 meters).

" " A long-distance bomber similar to this B-47 Stratojet dropped a bomb on a South Carolina farm in 1958. SuperStock/Getty Images

It was the height of the Cold War, when global powers vied for nuclear dominance. But it was an oops for the ages. Not only did the Gregg girls and their cousin narrowly miss becoming the first people killed by an atomic bomb on U.S. soil, but they now had a hole on their farm in which they could easily park a couple of school buses. Their garden ceased to exist; the playhouse seemed to have disappeared into thin air, save a small piece of tin from the roof; and the family home sat at a tilted angle, no longer flush with the foundation, surrounded by parts of itself.



One Serious Bomb

The Mark 6 bomb that fell onto this remote area of South Carolina weighed 7,600 pounds (3.4 metric tons) and was 10 feet, 8 inches (3.3 meters) long. With a maximum diameter of 61 inches (1.5 meters), the Mark 6 had an inflated, cartoon-like quality, reminiscent of something Wile E. Coyote would order from the ACME Co. Its capabilities, however, were no laughing matter.

Earlier that day, a specialized crew was part of a training exercise that would require the bomb to be loaded into an airplane and flown from Savannah, Georgia, to England. As the mock mission, detailed in this American Heritage account, began, it took more than an hour to load the bomb into the plane. After placing the bomb into a shackle mechanism designed to keep it in place, the crew had a hard time getting a steel locking pin to engage. They solved the issue by lifting the weight of the plane's bomb shackle mechanism and putting it onto a sling, then hitting the offending pin with a hammer until it locked into position.

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The mission was being timed, and the crew was under pressure to catch up. Following regulations, the captain disengaged the locking pin from the nuclear weapon so it could be dropped in an emergency during takeoff. When the airplane reached altitude, he tried to re-engage the pin from the cockpit controls, but because of the earlier makeshift solution, it wouldn't budge. The pilot asked the bombardier to leave his post and engage the pin by hand — something the bombardier had never done before. In fact, he didn't even know where the pin was located. After searching for more than 10 minutes, he pulled himself up to look over the bomb's curved belly.

Unfortunately, as he was trying to steady himself, the bombardier chose the emergency bomb-release mechanism for his handhold. The nuclear bomb immediately dropped from its shackle and landed, for just an instant, on the closed bomb-bay doors. Above it, the bombardier's body made an X as he hung on for dear life. As he scrambled to safety, the atomic bomb broke open the doors in the belly of the plane, and dropped straight onto the Greggs' farm.



The Chickens Were Vaporized

On the ground, all five members of the Gregg family were injured, as was young cousin Ella, who required 31 stitches. It wasn't until the family was recuperating at the home of the family doctor that evening that they learned that the source of destruction had been a bomb dropped by the U.S. Air Force.

Their home was no longer inhabitable and their outbuildings had been destroyed — even the family's free-range chickens had been utterly wiped from the face of the South Carolina farm. The blast was so powerful it cracked windows and walls in the small community of Mars Bluff, about 5 miles (8 kilometers) away from the family farm.

But what about the radiation? All the terrible aftereffects of dropping an atomic bomb? Why didn't the area sink into a nuclear winter, and why not rope off South Carolina for the next several decades, or replace the state flag's palmetto tree with a mushroom cloud?

" " A mushroom cloud expands above the Pacific atoll of Mururoa in 1971, following a French test explosion Galerie Bilderwelt/Getty Images

Herein lies the silver lining. The atomic bomb was not fully functional. It had been "safed" for transport, meaning that the radioactive part of the bomb's payload was removed and was being moved in a different plane.

In the 1950s, nuclear weapons had a trigger that compressed the uranium/plutonium core to begin the chain reaction of a nuclear explosion. Nuclear bombs like the one dropped on the Greggs could be set off, or triggered, by concussion — like being struck by a bullet or making hard contact with the ground. In the Greggs' case, the bomb's trigger did explode and cause damage. If the nuclear components had been present, catastrophe would have ensued.

Today, military-grade nuclear weapons can take more knocking around without exploding. In fact, accidents like that at Mars Bluff caused the Air Force to make changes. No longer could a nuclear weapon be set off by concussion; it would require a specific electrical impulse instead. And within days of accidentally dropping a bomb on U.S. soil, the Air Force published regulations that locking pins must be inserted in nuclear bomb shackles at all times — even during takeoff and landing.



The Aftermath

As for the Greggs, they never returned to life in the country. With the $54,000 they received in damages from the Air Force — which in 1958 had about the same buying power as $460,000 would today — the family relocated to Florence, South Carolina, living in a brick bungalow on a quiet neighborhood street.

"Not too many people can say they've had a nuclear bomb dropped on them," Walter Gregg told local newspaper The Sun News in 2003. "Not too many would want to."

The Greggs remained in touch with the crew, who reportedly felt badly about dropping a bomb on them. For years, crew members continued to correspond with the family via letters, and one even visited the family for a week's vacation decades after the incident.

In 1977, the Greggs sold the 4 acres (2 hectares) that had been their home site. From the road, there is little evidence that it had once been the site of an Air Force bombing, aside from a small roadside historical marker on U.S. Route 301. To reach the site you have to travel into an abandoned space that once housed a trailer park, and walk through an overgrown path that leads to what remains of the crater, significantly smaller, usually full of stagnant water and now marked by a plywood sign.

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