Eugene Stoner was an unassuming family man in postwar America. He wore glasses and had a fondness for bow ties. His figure was slightly round; his colleagues called him a teddy bear. He refused to swear or spank his children. “Boy, that frosts me,” he’d say when he was upset. He liked to tweak self-important people with a dry sense of humor. He hated attention.

A lifelong tinkerer and a Marine veteran, he was also fascinated by the question of how to make guns shoot better. When an idea came to him, he scribbled it down on anything he could find—a pad of paper, a napkin, the tablecloth at a restaurant. He had no formal training in engineering or in firearms design. Yet it was inside Stoner’s detached garage in Los Angeles, during the 1950s, that the amateur gunsmith, surrounded by piles of sketches and prototypes, came up with the idea for a rifle that would change American history.

Today, this weapon is the most popular rifle in America—and the most hated. The AR-15 is a symbol of Second Amendment rights to millions of Americans and an emblem of a violent gun culture run amok to millions more. With a lightweight frame and an internal gas system, the military version can be fired as an automatic, unleashing a stream of bullets from a single pull of the trigger, or as a semiautomatic, allowing for one shot per trigger pull. The civilian semiautomatic version is now the best-selling rifle in the country; more than 20 million such guns are in civilian hands. And it is a weapon of choice for mass shooters—including the white supremacist who killed three Black people last month at a store in Jacksonville, Florida, armed with a handgun and an AR-15-style rifle emblazoned with a swastika.

[Juliette Kayyem: The Jacksonville killer wanted everyone to know his message of hate]

The consequences of the AR-15’s creation have coursed through our society and politics for generations in ways that Stoner never foresaw. He created the gun with a simple goal: to build a better rifle for the U.S. military and its allies during the Cold War. He wanted to protect the country he loved. Now his invention is fused in Americans’ minds with the horror of people going about their daily tasks—at school, the movies, the store, a concert—and suddenly finding themselves running for their lives. Few of the participants in America’s perpetual gun debate know the true, complicated history of this consequential creation—or of the man behind it. The saga of the AR-15 is a story of how quickly an invention can leave the control of the inventor, how it can be used in ways the creator never imagined.

We interviewed Stoner’s family members and close colleagues about his views of his gun. They gave us insight into what the inventor might have thought about the way the AR-15 is being used today, though we’ll never know for sure; Stoner died before mass shootings with AR-15s were common. Later in life, after years of working in the gun industry, he was asked about his career in an interview for the Smithsonian Institution. “It was kind of a hobby that got out of hand,” he said.

As a boy growing up in the Coachella Valley, in Southern California, in the 1920s and ’30s, Stoner was fascinated by explosions. Before the age of 10, he had designed rockets and rudimentary weapons. On one occasion, he begged a friend’s father for a metal pipe and the local drugstore owner for magnesium. Stoner built a primitive cannon and pointed it at a house across the street, but before he could open fire, his father ran to stop him. “I told you to do this at the city dump,” scolded Lloyd Stoner, a veteran of the Great War who had moved the family to California from the farmlands of Indiana in search of a better life.

Eugene Stoner never went to college. He joined the Marines during World War II and was tasked with repairing weapons on aircraft in the Philippines. When he came home, he brought his wife, Jean, an adventurous woman who idolized Amelia Earhart, a special present: gun parts from Asia that he assembled into a rifle. She loved it. The couple often went hunting and shooting together. “He was a very quiet person,” Jean said in an unpublished interview that the Stoner family shared with us. “But if you talked about guns, cars, or planes, he’d talk all night.”

After the war, Stoner got a job as a machinist making aircraft parts. Every day after he came home, he would eat the dinner that Jean had prepared (beef Stroganoff was his favorite), take a quick nap, and then walk to the garage to work on his gun designs. Like other hobbyist inventors of the era, he believed he could move the country forward by the power of his ingenuity. “We were like the 1950s family. It was California. It was booming after the war,” his daughter Susan told us. “I knew from my dad—I felt from him—the future was wide open.”

[Conor Friedersdorf: The California dream is dying]

Stoner had the ability, common among inventors, to imagine engineering solutions that others stuck in the dogmas of the field could not. For centuries, gunmakers had built their rifles out of wood and steel, which made them very heavy. At the time, the U.S. military was searching for a lighter rifle, and Stoner wondered if he could build one using modern materials. If humans were soaring into the atmosphere in airplanes made of aluminum, he figured, couldn’t the lightweight metal tolerate the pressures of a gun firing? By the early 1950s, he had figured out how to replace one of the heaviest steel components of a rifle with aluminum. Then he devised a way of using the force of the gas from the exploding gunpowder to move parts inside the gun so that they ejected spent casings and loaded new rounds. This allowed him to eliminate other, cumbersome metal parts that had been used in the past. The first time he tried firing a gun using this new system, it blew hot gas into his face. But he perfected the design and eventually received a patent for it.

In 1954, Stoner got the opportunity to bring his radical gun concepts to life. That year, as Stoner later recalled, he had a chance encounter at a local gun range with George Sullivan. A relentless pitchman, Sullivan was then the head of a Hollywood start-up called ArmaLite, a subsidiary of Fairchild Engine and Aircraft Corporation whose mission was to design futuristic weapons. Impressed with the homemade guns Stoner was shooting, Sullivan hired him as ArmaLite’s chief engineer.

The small yet brilliant ArmaLite team worked at a fevered pace, designing a series of lightweight guns made of aluminum and plastic. Most went nowhere. Nevertheless, the ambitious Sullivan set the firm’s sights on an improbable target: the U.S Army’s standard-issue rifle. The Eisenhower administration’s “New Look”—an effort to rein in Pentagon spending and shift it toward newer technologies—opened the door for private companies to get big military contracts. The outsiders from Hollywood decided to take on Springfield Armory, the military’s citadel of gun making in western Massachusetts that had equipped American soldiers since the Revolutionary War. Springfield’s own efforts to develop a new rifle had resulted in a heavy wood-and-steel model that wasn’t much more advanced than the M1 Garand used by GIs in World War II.

Eugene Stoner, wearing his trademark bow tie, holds his creation the AR-10. The AR-15 was a scaled-down version of this gun. (Photograph courtesy of Susan Kleinpell via Farrar, Straus and Giroux)

ArmaLite’s first serious attempt at a rapid-fire rifle made of plastic and aluminum was the AR-10—AR for ArmaLite or ArmaLite Research (accounts differ), and 10 because the weapon was the company’s tenth creation. The rifle combined the efficient internal gas system Stoner had devised in his garage and lightweight modern materials with a design that made the gun easy to shoot and keep on target. In December 1956, Time heralded the AR-10 as a potential savior for the bumbling U.S. military and listed Sullivan as the gun’s inventor, a claim that infuriated Stoner’s wife. Sullivan had also meddled with the design, insisting that more aluminum be used in making the gun’s barrel, a move Stoner resisted. During military trials, the AR-10 fared poorly. At one point, a bullet erupted from the side of the gun’s barrel, just missing the hand of the soldier firing the weapon—and seemingly dooming ArmaLite’s chances of landing a military contract.

But within the Pentagon, a cabal of high-ranking officers led by General Willard Wyman launched a back-channel effort to save Stoner’s gun. Wyman was a legendary military leader who, at age 46, had joined the D-Day invasion at Omaha Beach as an assistant commander of the First Infantry Division. He knew that the United States needed better firepower as the Cold War flashed hot. America’s enemies around the globe were being armed by the Soviet Union with millions of rugged AK-47s that could spray bullets in automatic mode and were highly effective in guerilla warfare. Wyman was certain that modern wars would be won not by long-range marksmen but by soldiers firing lots of bullets in close combat. They needed a rifle that used small-caliber bullets so they could carry more ammo. And he was worried that the tradition-bound gun designers at Springfield Armory weren’t innovative enough to meet the challenge. When Wyman’s superiors brushed him off, he secretly flew to Los Angeles and stunned Stoner and his team by striding into the ArmaLite office unannounced. Wyman told Stoner that he wanted ArmaLite to build a new version of the AR-10 that fired a smaller bullet.

[James Fallows: Why the AR-15 is so lethal]

Stoner and an ArmaLite draftsman named Jim Sullivan (no relation to George) set about designing the gun. It was simple, efficient, and easy to use. Early versions of the AR-15 weighed just more than five pounds unloaded, less than the hedge trimmers and handheld vacuums of the era. With all of Stoner’s innovations—lighter material, fewer parts, and the gas system, as well as an in-line stock and a pistol grip—Jim Sullivan found shooting the prototype AR-15 to be easy, even after he flipped the selector switch to automatic. “That made it so well handling,” he told us. “If you’re firing full auto, you don’t want a gun that lifts.” Sullivan found the rifle’s recoil to be minimal. As a result, follow-up shots were quick when he switched it to semiautomatic. “It looked a little far-out for that time in history,” Stoner later said in the Smithsonian interview.

As Stoner and his backers sought to persuade the military to adopt the AR-15 in place of Springfield’s rifle, they were often met with skepticism about the gun’s small bullets. During secret military hearings about the rifle in the winter of 1958, Stoner explained to a panel of generals that the AR-15 had “a better killing cartridge with a higher velocity” than the Soviet AK-47. The generals asked Stoner how a smaller bullet fired from his rifle could do so much damage. “The wound capability is extremely high,” Stoner answered. “It blows up on contact rather than drilling a nice neat hole.” A slower .30 caliber round, similar to the one used by Springfield’s wood-and-steel rifles, “will go right through flesh,” but the faster, smaller bullet from the AR-15 “will tumble and tear,” he said.

Those in the military who wanted Springfield’s rifle to prevail tried to sabotage Stoner’s gun, rigging tests and shading reports so that it would seem like it wasn’t ready for the battlefield. During official trials in Alaska, Stoner arrived to find that the aiming sights on his guns had been replaced with bits of metal that were badly misaligned, causing soldiers to miss their targets. The guileless inventor was caught up in the murky world of Pentagon intrigue.

[From June 1981: James Fallows’s ‘M-16: A Bureaucratic Horror Story’]

Eventually, through persistence and luck, and with the help of a cast of lobbyists, spies, and analytics-driven military leaders, Stoner’s rifle would be adopted. At a key moment when it seemed that the AR-15 would be killed off by military bureaucrats, the powerful, cigar-chomping Air Force General Curtis LeMay, the architect of the U.S. bombing campaign in Japan during World War II, was asked if he wanted to shoot the gun. On July 4, 1960, at a birthday party for Richard Boutelle, the onetime head of Fairchild, the gun’s backers set up ripe watermelons as targets at Boutelle’s estate in western Maryland. LeMay fired, causing a red-and-green explosion. The general marched into the Pentagon soon after and demanded that the military purchase the weapon. It would become the standard-issue rifle—renamed the M16, for the prosaic “Model 16”—just in time for the rise of U.S. involvement in Vietnam.   

A U.S. Marine holds his M16 rifle alert after being fired on by North Vietnamese soldiers in the jungle southwest of Da Nang on April 22, 1969. (Yvon Cornu / AP)

In Eugene Stoner’s and Jim Sullivan’s minds, their work was not just intellectually engaging but also noble, a way to help America defeat the Communists. At school, in the 1950s, the Stoner children learned what to do in the event of a Soviet nuclear attack. Sirens and bells went off regularly, and teachers ordered kids to hide under their desks and cover their heads, Stoner’s daughter Susan recalled. For her father, the task of making the best rifle for the U.S. military wasn’t burdened with moral quandaries. Many weapons inventors at the time thought about the technical challenges of their weapons first, and wrestled with the consequences of their creations only afterward. “When you see something that is technically sweet, you go ahead and do it and you argue about what to do about it only after you have had your technical success,” J. Robert Oppenheimer, the lead developer of the atomic bomb, said almost a decade after bombs were dropped on Hiroshima and Nagasaki.

[From February 1949: J. Robert Oppenheimer’s ‘The Open Mind’]

After Stoner created the AR-15, he continued designing guns and artillery for a variety of gunmakers. Through a company he co-founded, he worked on antiaircraft weapons for the Shah of Iran, before the 1979 revolution scuttled the deal. He helped design a handgun for the venerable gunmaker Colt that the company tried to sell on the civilian market, without much success. But none of his creations came close to the prominence of the AR-15. By the 1990s, he’d become a superstar in the gun world. Royalties from the M16 made him wealthy; Colt, which purchased the rights to the gun from ArmaLite, sold millions of the weapons to the military. Stoner was “a Second Amendment guy,” his daughter said, but he didn’t talk much about the messy world of politics, either privately or publicly. He preferred thinking about mechanisms.

Throughout his life, Stoner was troubled by losing control over the production of his most famous gun. In the 1960s, as the U.S. ramped up production of the rifle for the war in Vietnam, a Pentagon committee made changes to the gun and its ammunition without proper testing. The results on the battlefields in Vietnam were disastrous. Stories of GIs dying with jammed M16s in their hands horrified the public and led to congressional hearings. The shy inventor was called to testify and found himself thrust into an uncomfortable spotlight. Declassified military documents that we reviewed show that Stoner tried in vain to warn Pentagon officials against the changes.

Stoner paid far less attention to the semiautomatic version of his rifle that Colt began marketing to the public in the 1960s as “a superb hunting partner.” Even after Stoner’s patent expired, in 1977, the rifle was a niche product made by a handful of companies and was despised by many traditional hunters, who tended to prefer polished wood stocks and prided themselves on felling game with a single shot. But the rifle’s status shifted after 9/11. Many Americans wanted to own the gun that soldiers were carrying in the War on Terror. When the 1994 federal assault-weapons ban expired after a decade, the AR-15 became palatable for mainstream American gunmakers to sell. Soon, it was a symbol of Second Amendment rights and survivalist chic, and gun owners rushed to buy AR-15s, fearful that the government would ban them again. By the late 2000s, the gun was enjoying astounding commercial success.

AR-15 style weapons are displayed for sale at the 2022 Rod of Iron Freedom Festival, an open-carry event to celebrate the Second Amendment, in Greeley, Pennsylvania. (Jabin Botsford / The Washington Post / Getty)

When Stoner died from cancer, in 1997, obituaries hailed him as the inventor of the long-serving military rifle; they made no mention of the civilian version of the weapon. Stoner left clues about his thoughts about the gun in a long letter, sent to a Marine general, in which he outlined his wishes for his funeral and burial at Quantico National Cemetery, in Virginia. He saw the creation of a rifle for the U.S military as his greatest triumph. He didn’t mention the civilian version. The government had wanted a “small caliber/high velocity, lightweight, select fire rifle which engaged targets with salvos of rounds from one trigger pull,” Stoner wrote. “That is what I achieved for our servicemen.”

[Ryan Busse: The rifle that ruined America]

The inventor wouldn’t get to control how his proudest achievement would be used after his death, or the fraught, outsize role it would come to play in American society and politics. Since 2012, some of the deadliest mass shootings in the nation’s history—Sandy Hook, Las Vegas, Sutherland Springs, Uvalde—have been carried out by men armed with AR-15s. Now children practice drills to avoid being gunned down by attackers with AR-15s at their school.

The last surviving member of that ArmaLite team, the draftsman Jim Sullivan, was at times haunted by the invention’s later impact. When we visited him at his workshop in Arizona in 2019, Sullivan pulled out the original drawings for the AR-15 and smiled broadly as he described how he and Stoner had designed the gun. He picked up parts to demonstrate how it worked, explaining its functions like an excited professor. He was proud of the weapon and loved Stoner. He said that his years working at ArmaLite were the best of his life. After hours of talking about barrels, bolts, receivers, and Stoner’s gas system, he paused and looked down at the floor. He said he’d grown deeply disturbed by the violence being wrought with the invention he had helped create. He said that mass shooters wouldn’t be able to do what they do without weapons such as the AR-15.

“Every gun designer has a responsibility to …” he said, pausing before finishing his thought, “to think about what the hell they’re creating.”

This article has been adapted from Zusha Elinson and Cameron McWhirter’s book, American Gun: The True Story of the AR-15.