While American nationality has always been a desirable asset in Juárez, it has become much more valuable — sometimes a matter of life and death — since the drug violence erupted in earnest three years ago. The children delivered at Casa de Nacimiento on the day we met would eventually be able to attend better schools, find better jobs and, if necessary, seek haven. I met a couple named Graciela and Milo, who brought their 2-week-old daughter, Jennifer, to Arnold’s birth center for a postpartum checkup. The parents were Mexican citizens. (For reasons of privacy, the center insisted that their last names not be used.) Their first two children were born in their home country, but when it came time to have this one, they decided to cross over.

Milo, a long-haul trucker who drives a route to Tijuana, said he just didn’t feel safe anymore, as the conflict between the narcos degenerated into anarchy. Graciela, who was sitting with the infant wrapped in a blanket on her lap, said she wanted Jennifer to have better options when she got older. Left unsaid was the underlying assumption: that Mexico’s crisis would stretch far into the future and that life for the vulnerable would become only more treacherous and exposed.
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Young Pepé Yanar stood in the glow of neon at a bar, his hair stylishly mussed, a gold cross dangling in the crook of his V-neck. “Everybody here is from Juárez,” he said as he surveyed the place, one of many that have opened on the well-to-do west side of El Paso over the last year or so. The Texan side of the border has traditionally been considered dowdier and strait-laced; Juárez used to be where Mexicans and Americans alike went for rollicking nightlife. But now many of its restaurants and clubs are closed, emptied by the violence, burned down by extortionists or cleared away by a dubious downtown renewal project.

Pepé told me about the event that drove out his own family: in November 2009, his father, José Yanar, was kidnapped as he made his way home from work for a dinner celebrating his 52nd birthday with his family. The kidnappers called, threatening to return his father in pieces if they did not receive a ransom of several hundred thousand dollars. Miraculously, José escaped — he still has a semicircular scar on his arm where the kidnapper he grappled with bit down hard — and immediately the whole family piled into a car and raced over the Paso del Norte bridge, abruptly severing themselves from their previous lives.

The Yanar family is in the furniture business, and they had never considered themselves vulnerable to Mexico’s violence. Pepé, his parents and his siblings were U.S. citizens, having been born in the United States, like the children of Casa de Nacimiento. Even though the family lived in Juárez, Pepé went to high school in America and then on to the University of Texas-El Paso, which offers in-state tuition to eligible Mexican residents. He and his friends spoke English and Spanish interchangeably, and they moved with assimilated ease on both sides of the border.

“The nature and the cause of violence in Mexico is driven in part by the border itself,” says David Shirk, director of the Trans-Border Institute at the University of San Diego. “They’re fighting for control of access to the other side. So to me, violence stops at the border because the need to control territory stops at the border. It’s about real estate, and it’s about corruption networks.”

Although reliable figures are hard to come by, the Internal Displacement Monitoring Center estimates that some 230,000 Mexicans have fled the violence, about half of them to the United States. While illegal immigration to the United States has dropped over all by about 80 percent from the mid-2000s because of tougher enforcement and the effects of the recession, border cities have seen a contrary phenomenon. Since 2009, according to the Census, the El Paso metropolitan area’s population has grown to around 800,000 residents, up by 50,000, an undetermined but significant percentage of them coming from Juárez. Some have sneaked across the river and are thus difficult to count. Many others, however, have made the trip legally, at least initially, coming over the Rio Grande bridges on border-crossing cards — the short-term visas are easy to overstay — or via a program that offers green cards to foreign investors and their families, as long as they create at least 10 jobs.

José Yanar opened a furniture store called Designer World on Texas Avenue, just off Interstate 10. He and his son both work there, coordinating orders with the family’s factory, six miles away in Juárez, which they hadn’t visited in 18 months. I visited Designer World one day and found the elder Yanar — a bluff, barrel-chested boss nicknamed Pelón (Baldy) by his employees — in an office next to the showroom, where he was keeping watch over the factory on a large flat-screen television that was divided into 16 quadrants, each of which was streaming a jerky feed from a closed-circuit camera. Periodically one of his several phones would screech, and José would carry on his daily business in Spanish with the walkie-talkie voice of a factory manager.

“The people that I have there working for me, they’re very loyal, and of course I pay them a little bit more,” José said. Still, running a business from afar involves all sorts of annoying inefficiencies. He was afraid to set foot in Juárez, but not all of his managers had U.S. visas. So when he had to see them in person, he sometimes conducted meetings at the center of a border bridge, in the buffer zone beneath the Mexican and American flags.

After José escaped his kidnappers, the whole family crowded in with a sister-in-law who already lived in El Paso, and they put their place in Juárez on the market. “I still hope I can sell it,” he said. “But every single house in Juárez is for sale.” Compared with what others were going through, though, these were minor hardships. Yanar purchased a house in El Paso, and soon he found his neighborhood was full of people he knew from the other side. His social life picked up. He didn’t have to worry about his kids sneaking back into Juárez, because most of their friends had moved, too.

“Never mind,” Ana said. “We’re not from Juárez anymore.”

Sometimes I wonder what El Paso lives off of,” says Tony Payan, a professor of political science at UTEP. To a large extent, the answer is that it subsists off of Juárez. There’s no real agriculture in its arid climate, and much of the city’s once-significant industrial sector has closed down or moved away. El Paso’s income and education levels have long been far below the national average. For the last few decades, the city’s prosperity has been tied to production in the maquiladoras, the outsourced manufacturing industry across the border, and to public-sector employment in border security, law enforcement and at the fast-growing Army base at Fort Bliss — institutions that are all there, to one degree or another, because of the city’s proximity to Mexico. Then, of course, there’s the hidden economy of the narcotics trade, which generates anywhere between $6 billion and $36 billion a year, depending on whose estimates you credit.

Howard Campbell, an anthropologist who studies drug trafficking, told me that the relationship between the two cities “is both symbiotic and parasitic.” When I asked him who was the parasite, he gave me an amused look — silly outsider — and said, “The U.S.”

Local lore holds that one city was built on the other’s misfortune. Major battles of the Mexican Revolution were plotted in El Paso and fought in Juárez. When warfare broke out in the streets of the Mexican city in 1911, a newspaperman later recalled, “El Paso was delighted and moved en masse down to the riverbank to watch the scrap.” El Paso’s bank deposits increased by 88 percent in just a few years, as merchants made fortunes supplying all the warring parties. One hardware store sold barbed wire to the Mexican government and wire cutters to the rebels.

David Dorado Romo, a historian and the author of “Ringside Seat to a Revolution,” compares El Paso in that formative period to Berlin during the Cold War. One downtown building served as a revolutionary headquarters, while counterspies kept an office down the street. The rebel leader Pancho Villa, a teetotaler, held court over ice cream at the Elite Confectionery. Many noncombatants also took shelter on the American side of the river. By 1920, El Paso had doubled in size, to around 80,000 people. Displaced members of the Mexican elite drove a housing boom, opened stores and named a street for Porfirio Díaz, their deposed dictator. One revolutionary would later write that the border region was filled with “men without a country . . . who are foreigners in both lands.”

Since Romo’s book appeared in 2005, there has been a surge of local interest in this era, coinciding with the election of a generation of young reformist politicians who appreciate what came out of it: some architecturally significant buildings, a wise city plan and the dim memory of a moment when El Paso played a momentous role. This has a lot to do with why, when Juárez erupted, the mood in El Paso wasn’t entirely mournful. “We’re stuck in this circular historical pattern,” says Veronica Escobar, a 41-year-old New York University graduate who is El Paso County’s judge, its highest elected official. “Here we are 100 years later, and again there’s this horrible, bloody war happening again across from us.” And yet Escobar’s sympathies, like those of many others, are tempered by a sense of recapitulated opportunity. “We benefit,” she says.
 

Juárez’s murders are terrifying in both their sheer numbers and their grisly impunity: beheaded bodies are left on busy streets, hit men open fire into crowds in broad daylight. “The problem is that our crime is disorganized,” one prominent Mexican lawyer told me. “If it was organized crime, we wouldn’t see it.” Though the lawyer’s family stays in El Paso, he is part of the dwindling population that still crosses to Juárez for work. Like many others, he takes steps to limit his exposure, traveling at irregular times, exchanging his BMW for a less conspicuous car. (For obvious reasons, he wouldn’t allow his name in this article.) Everyone who spends time in Juárez seems to espouse a contradictory theory of risk management: I’m blond; they won’t touch an American. . . . I look Mexican; I blend in. . . . I drive a very fast car. . . . I only take taxis. . . . I look harmless. . . . I look tough. . . . Don’t worry, everyone knows who I am. . . . Don’t worry, nobody knows who I am.

Over coffee, I asked the leaders of La Red what strategies they used to manage the threats. Yanar looked incredulously at Mauricio, who still keeps an office in Juárez, and joked, “He likes the dangers.” Mauricio lay a rosary on the table. “This is my policy,” he said.

I’m not a prayerful man, so the first time I crossed the border, I did it in what everyone said was the safest possible way. I went over with a maquiladora executive. Pancho Uranga is a voluble, buzz-cut man who works with Foxconn, a Taiwanese maker of electronic components, and helped establish its brand-new plant.

“Right now we’re in the U.S.,” Uranga said, striding over the invisible line. “And right now, we’re in Mexico. Nobody’s gonna check your passport.”

And no one did. On the Mexican side of the Santa Teresa border crossing, just outside El Paso, we hopped into a white van that was waiting for us and drove right past a couple of disinterested border guards. Foxconn chose to build its facility out on the far western outskirts of Juárez.  “Initially it was hell,” Uranga said. “There was nothing out here but rabbits and snakes.” The maquiladoras have been largely untouched by the violence, but isolation added an extra buffer. “It gave us a clean piece of paper so we can design everything from scratch,” he said. “You feel secure here, versus driving through the city in today’s environment.”

An Asian company opening a plant in North America marks a reversal, to say the least. The maquiladora industry grew in response to a United States government decision in the 1960s to drastically limit the number of Mexicans crossing the border for seasonal farm work. Mass unemployment followed, and Mexico enticed American manufacturers to new free-trade zones along the border, shielded from United States taxes, unions and wage requirements. The industry crested shortly after Nafta was ratified, and for the last decade it has been struggling to compete with the even less expensive factories in Asia. The financial crisis vaporized about a third of Juárez’s 250,000 factory jobs in less than two years. But with costs and inflation rising in China, Mexico is once again able to market a comparative advantage. There is a catch, however. “Putting plants into places where drug lords are fighting is not something that companies want to do,” says Harold Sirkin, a senior partner with the Boston Consulting Group.

Foxconn’s secure facility, which produces desktops and laptops for Dell, is like “a prison with a campus,” Uranga said. Its landscaped grounds are surrounded by walls and razor wire. Managers stay in adjacent dormitories while workers come in from surrounding areas on white school buses. Uranga said the pay at the plant was around the average for the maquiladora industry, about $80 a week.
 

Some doubt Uranga’s theory that the outsourcing industry benefits the poor. They suggest that it’s hardly a coincidence that plants like his and the drug industry exist side by side. “To what extent does the very nature of the industry contribute to the patterns of social anomie and violence that we see in Juárez and elsewhere along the border?” asked David Shirk of the Trans-Border Institute. The maquiladoras provide low-skilled jobs, but their existence has made Juárez a destination for the rootless and the desperate. This population appears to have been susceptible to the richer promises of the drug trade, as well as to the lure of illegal immigration to the United States, with its comparatively well-paid opportunities.

The migration of the last three decades, primarily driven by economic disparity, has left a permanent mark on America — and Southwestern states like Texas most of all. Hispanics accounted for two-thirds of Texas’s substantial growth over the last decade, according to Census figures, and now make up 38 percent of the state’s population.

“The Hispanic phenomenon in this country is totally underappreciated and underserved,” Bill Sanders, an El Paso real estate investor, says. “It’s one of the main drivers for job and economic growth.” An avuncular, white-haired grandee of the Texas borderland, Sanders is one of the most influential figures in a region ruled by mercantile interests. (He is, incidentally, also the father-in-law of Beto O’Rourke, the El Paso politician.) Among many holdings, Sanders is a founder of the Verde Group, which owns millions of square feet of industrial property in and around El Paso and Juárez, and 22,000 mostly undeveloped acres facing the Foxconn plant from the American side. Sanders is bullish on the border’s potential. “It’s such a powerful generator of value,” he says. “The United States is the largest consumer market in the world, and the most efficient place in the world to produce those goods is on the U.S.-Mexican border.”

Sanders made his name in Chicago real estate before moving back to his hometown of El Paso a decade ago with a notion about remaking the city’s identity. “In 2001, a group asked me to meet the mayor, and he wanted me to redevelop downtown,” he told me. Back in Chicago, Sanders had been a member of the Commercial Club, a private organization that quietly influences the city’s urban planning. So Sanders helped put together a similar organization called the Paso del Norte Group, which embarked on a hushed process of drawing up a plan for restaurants, loft apartments and a shopping center. When Sanders went public with the idea, though, and formed a private investment vehicle to buy up property, local advocates accused the developer of trying to bulldoze the Segundo Barrio, El Paso’s old immigrant neighborhood.

The controversy took on divisive overtones of race and class, especially after the Paso del Norte Group released its private membership list under pressure from activists and a news Web site. It included prominent family names from both El Paso and Juárez and was the clearest possible expression of the intermingled political and financial interests that have long dictated the course of development on the border. “They marry each other, they socialize with each other,” Tony Payan, of UTEP, says. “For them, citizenship means nothing. The border does not exist.”
 

Suddenly, flashing lights appeared behind us. It was a Border Patrol agent in a truck, chasing behind the Mexican C.E.O. on his A.T.V., suspicious of our purposes.

After IDs and explanations were produced, we continued on our way westward, ending up at Sanders’s ranch in Columbus, a grungy border outpost that’s famous for two things: being attacked by Pancho Villa a century ago and, earlier this year, having its mayor and police chief arrested for gunrunning to the cartels. We returned home along a two-lane road that hugged a low, metal barricade marking the border. Every few miles, we passed another white S.U.V., and someone in the car would mutter, “La Migra,” the colloquial name for the Border Patrol. The force has doubled in size around El Paso over the last few years, at the same time as the number of Mexicans trying to cross has dropped, meaning limited stimulation for those on watch. As we turned off the road to take a closer look at the wall, we passed an agent sleeping soundly behind the wheel of his vehicle.

On our way back up from the borderline, the agent woke up, startled. He rolled down his window and asked, “Where’d you guys come in through?”

El Paso’s population is 80 percent Hispanic, but when the Juárez refugees began flooding in, the reaction from some quarters was far from brotherly. One day, José Yanar told me, a man came knocking on doors in his new neighborhood in El Paso. He presented a petition to one of Yanar’s Mexican neighbors. “He says: ‘Can you sign this paper? These stupid Mexicans are coming here and buying houses.’ ” Yanar was flabbergasted: in most of recessionary America, no one was buying houses, but in El Paso sales and prices have held fairly steady, in part because of people like him. He thought that would make Americans happy, but everywhere it seemed as if politicians were bent on driving Mexicans out.

Across the country, conservatives were using the spectacle of violence in Mexico to push draconian immigration and border-security measures. Last spring, as Rick Perry, the governor of Texas, began flirting with a run for the Republican presidential nomination, he took Fox News’s Greta Van Susteren on a trip down to the Rio Grande. He told her there was “great terror on our southern border” and called the status of security an “absolute national disgrace.” At Perry’s urging, the Texas Legislature spent much of the spring debating a proposal to push local police units to enforce federal immigration laws.

The measure eventually failed, but it dominated the political discussion in the borderland, where people saw it was just one facet in a larger surge of xenophobia. To most people who actually live in El Paso, Perry’s assertion that they are undefended is a bit of a joke. If anything, the city has the feel of an armed camp. Helicopters hover low over the Rio Grande, surveillance drones circle high above and there’s the hulking border fence. In May, President Obama stood a few hundred feet from the border in El Paso and declared that the nation has “more boots on the ground on the southwest border than at any time in our history.” When he mentioned the fence, the audience booed.

Sitting in the audience that day, shaded by a straw hat, was the Rev. Arturo Bañuelas, pastor of the St. Pius X parish on the east side of El Paso. “I was one of the ones booing,” Father Bañuelas later told me. He was disappointed by what he saw as Obama’s ineffectual advocacy of immigration reform and his comparatively vigorous approach to enforcement. Deportations have increased under Obama, even as the drug conflict has worsened. Of the thousands of asylum claims filed by Mexicans last year, only 49 were granted.
 

Nearly everyone I met in El Paso — whether they spoke Spanish or English, were liberal or conservative, rich or poor — told me the same thing: no one outside really understood this crisis they were living through. American politicians often talked about the evils of the cartels as if drugs were a purely Mexican business, instead of a thriving multibillion-dollar trade that involves two parties. A generation-long effort to stanch the flow of drugs and desperate people across the border had reached its logical endpoint, the approach favored by ancient empires: the raising of a wall. The barrier wasn’t very likely to overturn the law of supply and demand, but it did serve as a useful symbol of the process of alienation, a closing-off of lives and minds, along the line it traces. The peculiar fluidity of the borderland was drying up as it was slowly sapped away by two unappeasable forces: the cartels on one side, the reactionaries on the other.

Still, the tattered ideal of a world without borders holds great power. One day in February at Casa de Nacimiento, a group of 10 pregnant women sat sprawled on the floor of a carpeted room, listening as a woman named Luz Chavez gave an introductory birthing class. Chavez is Linda Arnold’s most trusted assistant and someone who understands the unique needs of the clientele. Though she was born in America — her mother was a Casa de Nacimiento client — she still commutes across from Juárez. In addition to the usual explanations about fetal development and diet, Chavez crisply covered the rules for navigating the law’s gray areas: visas, how to respond to probing questions at the border, handling the application for a birth certificate. “We try to teach them that they can have an American baby, but they have to pay for it,” Chavez said afterward, adding with a nervous smile, “we’re not doing anything illegal — so far.”

There were troubling rumblings, though, emanating from Washington and Austin. In one of the most extreme expressions of nativist fury, conservative talk-show hosts and Tea Party politicians had taken to fulminating against “anchor babies,” suggesting that a horde of devious Mexican mothers was slipping into the United States to give birth and cheat the system. In reality, having American offspring is not a shortcut to naturalization — children cannot petition for their parents to become permanent residents until they turn 21 — but the misinformed rhetoric proved powerful. “They’re talking about these anchor babies, illegal immigrants, but these are not illegal immigrants,” Arnold said. “They are legally doing what they can do.”

When I returned to Casa de Nacimiento in May, Arnold seemed weary of her newly controversial enterprise. In the months since my last visit, local authorities in San Gabriel, Calif., had closed down a maternity center catering to Chinese visitors, ostensibly for building-code violations, and Republicans in Congress and the Texas Legislature were proposing to curtail birthright citizenship, on constitutionally dubious grounds. Because they were not born in hospitals, some Casa de Nacimiento children were now finding their citizenship claims subjected to extreme scrutiny. And while Juárez’s violence gave women every incentive to secure their children a U.S. passport, they still had to contend with the immediate obstacles of the border. Increased security meant long lines and uncomfortable waits for a woman in labor. “It can be based on problems in Mexico with the narcos, it can be the U.S. Border Patrol, it can be both,” Arnold said. The phenomenon that originally drew her to El Paso, the free flow of expectant mothers across the border, had given way to discouragement and ever-firmer demarcation.

Arnold said her client base had fallen about 50 percent from its peak a decade or so ago. The harshest blow was economic: Mexico’s upheaval might be buoying El Paso’s economy through the recession, but Juárez was suffering as manufacturing struggled and its population dispersed because of fear. “People who were working at the maquilas for $50 or $70 a week are now part-timers at $30 a week,” Arnold said. This illustrated something economists told me when they predicted that the stimulating jolt to El Paso was likely to be short-lived: the longer view of history suggests that the cities rise and fall together, if not always in perfect unison. Their fates can never be disentangled.

Earlier this month, after running her business for 26 years and training more than 800 midwives, Arnold decided with great sadness to close it. Over the course of its existence, she estimates, Casa de Nacimiento delivered some 13,400 new Americans. “They now have the best of both worlds,” Arnold said. In a metropolis divided by a river, and so much else, the midwife had bequeathed them a bridge to the other side.