What causes a man to commit an act as monstrous as the Oklahoma City bombing? There are conventional, and useful, explanations for why Timothy McVeigh detonated a truck bomb in front of the Alfred P. Murrah Federal Building on April 19, 1995, killing 168 people, including 19 children. A troubled upbringing with a mother who abandoned him. A loss of social status as the factory jobs where his father and grandfather worked disappeared from the Buffalo of his youth. Anger at women who spurned him as he became an incel—an involuntary celibate—before the term existed. Above all, rage at Blacks and Jews, and especially at President Bill Clinton’s federal government.

The remains of the Alfred P. Murrah Federal Building, in Oklahoma City, on April 19, 1995.

But as I researched a book on the bombing, over the past several years, I came up with an additional reason. McVeigh and his co-conspirator, Terry Nichols, were also shaped by a region and its haunting landscape. The bombing was rooted in Kansas, specifically a series of towns along Route 77, a two-lane blacktop in the north-central part of the state known as the Flint Hills.

McVeigh’s name is forever linked to Oklahoma City. Strangely, though, before the bombing, McVeigh had no particular connection to the place. He never lived in Oklahoma City or even spent a night there. For a man who designed and built a bomb with enormous care, McVeigh chose the Murrah building as his target in an almost haphazard way. Kansas, much more than Oklahoma, shaped him.

McVeigh and Nichols met on the first day of army basic training in 1988, when McVeigh was 20 and Nichols was 33. After completing basic, both were assigned to Fort Riley, a historic outpost adjacent to Junction City, in the Flint Hills.

Terry Nichols, McVeigh’s co-conspirator, after being charged.

Riley has been an army base since before the Civil War. George A. Custer, of Custer’s Last Stand, had been stationed there. By the 20th century, Riley was known as the home of the First Infantry Division—or the “Big Red One,” for the red numeral on its insignia. That division had played a storied role in major combat operations, and when McVeigh and Nichols arrived, it was a leading training center for mechanized warfare.

The terrain of the Flint Hills, which includes Junction City and a handful of small towns to the south, is well suited for tanks but little else. The forbidding landscape of rolling mounds and rocky soil, largely devoid of trees and carpeted with native grasses, has resisted many attempts to cultivate and settle it over the decades. There’s some agriculture, some grazing, and a lot of empty space. Like most of Kansas, the people of the Flint Hills are overwhelmingly Republican, but it’s the absence of people, more than their partisanship, that’s most evident.

As one local historian observed, “Jobs have largely migrated to a handful of nearby cities … leaving behind a smattering of shrinking towns with gap-toothed Main Streets and abandoned farm machines rusting in fallow fields.” The land has a ghostly quality, and it’s not hard to imagine how dark thoughts might fester in the bleak territory.

The Flint Hills of Kansas.

From his late teens, McVeigh was obsessed with the dystopian novel The Turner Diaries, written by the neo-Nazi William Luther Pierce III. In the story, the government has been taken over by an evil conspiracy of Blacks and Jews who move first to confiscate private firearms under a law known as “the Cohen Act.” Earl Turner, the hero and narrator, sets off a truck bomb by the F.B.I. building, which inspires a broad rebellion against the government as well as a full-fledged race war. McVeigh intended his bombing of the Murrah building to be not just an imitation of Turner’s act but also a prompt for a similar rebellion against Clinton’s federal government.

It’s the absence of people, more than their partisanship, that’s most evident.

So McVeigh came to the military already with an inclination toward white supremacy, right-wing fanaticism, and vigilante violence. His extremism grew and festered as a soldier.

McVeigh made a name for himself at Fort Riley. He was fastidious about his appearance, always wearing creased trousers, shined shoes, and polished brass, which earned him the nickname “Mr. Spotless.” He trained incessantly, even on his own time. He marched around the base carrying a heavy pack; he studied training manuals; he taught himself to disassemble and re-assemble weapons—blindfolded. One of his former commanding officers would later tell the F.B.I.: “I wish I had a platoon full of Tim McVeighs.”

Timothy McVeigh at his father’s home in the early 1990s.

Fort Riley was polarized along racial lines. Anti-white and anti-Black graffiti marred many walls. The racism that McVeigh began to express when he was growing up deepened in the army. As he later told his lawyer Stephen Jones, his complaints about Black people included “the loud rough music, the low riders together with bass music, the loudness in the barracks and everywhere else, the staying up and keeping others up all night, the playing of dominoes loud all night.”

McVeigh wrote to his childhood friend Steve Hodge from Fort Riley, “I used to call black people ‘black,’ because I only saw one side of the story. Now you can guess what I call them.” Fellow soldiers later reported to the F.B.I. that McVeigh was fond of the n-word and referred to Black children as “nig-lets.”

Newer to McVeigh’s political worldview was hostility to gender equality. Women always remained a foreign species, baffling and sometimes angering him. He later told his lawyers that he had had sex with women a handful of times (apparently never confirmed by any of the women), but he never had a girlfriend or even an actual relationship. At Fort Riley he was appalled when he saw women recruits.

“This was the first time that a female was assigned to our class,” McVeigh told Jones. “And it was just a joke. We had to post extra guards so she could go to the bathroom, she couldn’t pull her weight digging, she couldn’t carry the M-60 when it was her turn to be assigned to it. You started seeing that the infantry was no place for a woman.”

McVeigh’s extremism “grew and festered” at Fort Riley.

Many of McVeigh’s fellow soldiers chose to blow their salaries at strip clubs and bars in Junction City, which operated as a kind of commercial adjunct to Fort Riley. He agreed to be the designated driver for these outings, and his colleagues would cover the cost of his Cokes. McVeigh soon saw a business opportunity in teetotaling, and he started hiring himself out as a taxi service. Drunken soldiers would call his room in the middle of the night, and he’d show up in his car—for a price. McVeigh soon expanded his services: he’d do laundry, substitute for guard duty. Eventually he started lending money at loan-shark rates and earned another nickname: “the Jew.”

“I wish I had a platoon full of Tim McVeighs.”

McVeigh appeared to be a competent soldier, with a sideline as an industrious freelance assistant to his colleagues. But as he made clear in his letters to Hodge, there was anger simmering beneath the surface. “The influence of the Army and the people around me have changed/are changing me in many ways,” he wrote. “I now see a much larger portion of the whole picture including gang warfare, cocaine use, and the insignificance of law enforcement. I will never be the same.”

McVeigh saw the police as extensions of the overweening hand of government—a departure from conventional right-wing views, which tend to be pro–law enforcement. McVeigh came to regard law enforcement in a hierarchy of disdain, with his greatest tolerance for local authorities and his greatest hostility for the F.B.I., which he associated with the federal government. McVeigh arrived in the army predisposed to violent political action, but his experience enhanced and accelerated his radicalization.

In 1991, McVeigh was called up to fight in the first Gulf War, and he excelled. As a gunner on a Bradley Fighting Vehicle—a kind of cross between a tank and a troop carrier—McVeigh won a Bronze Star for taking out an Iraqi-troop encampment.

Timothy McVeigh’s Route 77

When he returned Stateside, in early 1992, he pursued his dream of joining the Special Forces by seeking to become a Green Beret. But he quickly failed the tryout and soon found himself demoralized and at loose ends. He was assigned again to Fort Riley but chose to live in a rented apartment in Herington, a forlorn former railway crossroads about 35 miles south, on Route 77. At that point, though, the thrill of army life was gone, so he took an honorable discharge, returned to his hometown of Buffalo, and worked as a security guard. There, he seethed at Bill Clinton’s election in November 1992.

In early 1993, McVeigh quit his job and took off on the road. He never again had a permanent home, instead living out of his Chevy Geo (“the Road Warrior,” he called it) and cheap motels. He scratched out a living selling what he could (including The Turner Diaries) at gun shows all over the country. During his long drives in this period, he became a loyal fan of Rush Limbaugh’s. He also reconnected with Nichols, who was living a similarly estranged existence in Michigan, and together they headed back to the Flint Hills.

McVeigh raged at Bill Clinton’s federal government.

Two events pushed them from alienation to action. On April 19, 1993, the F.B.I. raided the Branch Davidian compound outside Waco, Texas. An ensuing fire killed 76 people. Then, on September 13, 1994, President Clinton signed a bill banning the sale of assault weapons, which McVeigh saw as an assault on his constitutional rights. Like Earl Turner, McVeigh and Nichols would bomb a federal target, and, they hoped, ignite a counterrevolution.

They did their training and planning in the threadbare towns along Route 77. They robbed explosives from a quarry in Marion, where Nichols was living with his second wife, a mail-order bride from the Philippines, and working as a farmhand. To practice their marksmanship in the nearby fields, McVeigh procured a life-size silhouette as a target to which he pasted a photograph of Hillary Clinton’s face. After considering federal buildings in other cities as their target, the pair chose the one in Oklahoma City for a practical reason—they could park a truck right next to the front door and inflict maximum damage.

The Dreamland Motel off Route 77, where McVeigh spent his nights before the bombing.

They planned the attack for April 19, 1995, because it was both the second anniversary of the Waco raid and the date of the Battle of Lexington, in 1775. McVeigh fancied himself a kindred revolutionary with the Founding Fathers.

McVeigh and Nichols would bomb a federal target, and, they hoped, ignite a counterrevolution.

For their bomb, McVeigh and Nichols had bought thousands of pounds of fertilizer in farm-supply stores in the area and loaded it all into a storage locker in Herington. They had also bought three 55-gallon drums of racing fuel at a racetrack near Dallas, Texas, which they had learned would provide a more powerful blast than ordinary gasoline.

The Oklahoma bombing killed 168 people.

As the day drew near, McVeigh checked into the Dreamland Motel in Junction City. On April 17, he went to Elliott’s Body Shop, just outside downtown Junction City, and rented a 20-foot Ryder truck, which he parked overnight at the Dreamland.

Wired for a big day, McVeigh rose early the following morning to make yet another journey on Route 77. He drove 35 miles south, to Herington, where he and Nichols emptied the contents of the storage locker into the truck. Then they drove 13 miles north, back toward Junction City, to Geary State Fishing Lake, which was just off the road. Here, sheltered by a few trees, McVeigh and Nichols did the sweaty work of mixing the fertilizer and racing fuel in barrels. When it was done, McVeigh drilled a hole in the cab to thread a fuse to the back. It was the same method that had been used in The Turner Diaries.

McVeigh in a bulletproof jacket as he is escorted to court, 1996.

At last, they said their final good-byes, and McVeigh headed south on Route 77 toward Oklahoma City, about four hours away. The following morning, McVeigh lit the fuse with a Bic lighter and hustled behind a nearby building so he wouldn’t be consumed in the blast.

The planning for the attack, the purchase and storage of the ingredients, the rental of the truck, and the mixing of the bomb had all taken place around Route 77 in the Flint Hills. Likewise, McVeigh’s politics had hardened at Fort Riley, in the same part of Kansas. It’s not possible to know whether McVeigh would have bombed the Murrah building, or anything else, if he had chosen to settle in a more hospitable place. But it does seem clear that the toxic isolation of the Flint Hills pushed McVeigh toward the convulsion of April 19, 1995. His memory still haunts the quiet byway of Route 77, as well as the emptying towns by its side.

Jeffrey Toobin’s new book, Homegrown: Timothy McVeigh and the Rise of Right-Wing Extremism, will be published on May 2