“You’re the only gringo who’s come over the bridge today,” said Julián Cardona, a lean and sardonic journalist in Ciudad Juárez, where he has spent most of his working life reporting on its excesses. The excesses have included many beheadings. Yes, he told me later, there really were corpses in the streets and a body strung up on an overpass. “Juárez deserves its bad reputation, but you have to understand the reason why.”

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The border city of Juárez was notorious for achieving what is likely the 2010 world record for violent homicides—3,622 shootings, stabbings, lynchings and death by torture. “Don’t go there,” people say. Yet it’s next-door, and the number of murders annually has dropped to less than Chicago’s 468 homicides last year. (Earlier this year, Juárez was removed from the list of the world’s most violent cities.) When the wind is southerly the risen dust of Juárez can make you sneeze in El Paso. The cityscape twinkles at night; by day it is tawny brown and low-lying, scattered along the south bank of the Rio Grande, easily visible from its sister city across the river in Texas. You can sometimes hear its honking horns on the American side, and in its year of mass murder the rat-tat of gunshots was easily audible and some bullets fired in Juárez damaged El Paso’s buildings.

The river is theoretical here, just a concrete culvert tagged with indignant graffiti, a trickle of sour shallow water rippling through, like a wadi you might see in drought-stricken Syria, the surrounding hills just as sunbaked, sandy and Syrian. The contour of the culvert marks La Frontera, which has been much in the news.

Out of curiosity, a wish to see the city of the wicked superlative, I crossed one of three bridges on a day of dazzling April sunlight.

In contrast to peaceful and salubrious El Paso, Juárez is nearly all one-story dwellings, small concrete bungalows, flat-roofed and ruinous huts, and jacales—rough shanties—on an immense grid of broken stony roads, 1.3 million people, roughly 255,000 of them employed in the factories, the maquiladoras, most of them U.S.-owned. The Mexican employees generally work 9.5-hour shifts, for an average daily pay of $6 to $8. In spite of the hoopla about NAFTA, this does not translate to a living wage. Despite accounts of the city’s revival, Juárez still seemed hard-up, crumbling and bleak, with an anxious melancholy air of poverty and danger.

I had arranged to meet Julián Cardona at the café Coyote Inválido, next to the World Famous Kentucky Club & Grill, a once-boisterous and thriving bar, these days thinly visited and subdued.

“Maybe you’re the only gringo all week,” Julián added over coffee. Now he was laughing. “Maybe all month!”

Gringos don’t go to Juárez as often anymore, he said. (Although millions of Americans each year visit the country as a whole, many crossing through border towns.) They don’t seem to go to Nuevo Laredo, or Ciudad Acuña, or Reynosa or Matamoros, or many other border towns. I know that because I went to all of these.

**********

Juárez was the sixth Mexican city I’d visited on this trip, following (with necessary detours) the 1,989-mile border, America’s tattered fringe, from west to east. I had been hearing “I haven’t been there in years” since leaving the congestion of Tijuana. People begged me not to cross. I was to visit six more towns, before ending up at the easternmost point of the border beyond Brownsville and Matamoros, near the mouth of the Rio Grande, where the soupy green river pours into the Gulf of Mexico at the estuary just south of Boca Chica and its brown burgeoning surf.

My idea had been to drive along the border and cross whenever convenient to the Mexican side. These dozen crossings were a revelation to me, putting the entire border protection debate into perspective, giving it a human face—or rather many faces. It is at once more heartening and more hopeless than I had imagined—and I had felt somewhat prepared, having traveled to U.S. and Mexican Nogales four years ago. But nothing really prepares you for the strangeness of the border experience.

The first thing to know is that huge numbers of Mexican-Americans and Mexican nationals cross every day, in both directions. They have visas and passports, or an ID that allows them access. Renting or buying a house on the U.S. side is prohibitive for many, and so a whole cross-border culture has developed in which American citizens of Mexican descent live in a house or an apartment—or a simple shack—in a border city such as Juárez or Nuevo Laredo, and commute to work in El Paso or Laredo.

“I bought a house in Ciudad Acuña for less than twenty grand,” Roy, a car mechanic, told me in Del Rio, Texas, across the river. I heard this same tale many times. “I cross every day.”

As Julián Cardona noted, I may have been one of the few gringos who crossed the bridge to Juárez that day, but there were thousands of Mexicans hurrying to the U.S. side, who then returned to Mexico when their work was done. Many children in Nogales, Mexico, go to school in Nogales, Arizona. “Yes, I speak English,” I often heard in Mexico. “I was educated over the border.”

It is a fairly simple matter to walk to Mexico at any point, but there is always a crush of people—all of them with documents—waiting to enter the U.S., either to work, go to school, or buy clothes or electronics, which are much cheaper in the U.S. A busy, bilingual Walmart can be found on the U.S. side of most border crossings. There are always discount shops on the U.S. side; always discount pharmacies on the Mexican side, though the so-called Boys Towns—red-light districts for legal prostitution—see little roistering.

I found there is such a thing as a distinct border culture—border music, not just the narco-corridos, or drug ballads celebrating the frontier exploits of the Mexican cartels, but norteño music, northern border ballads. A border vocabulary has grown up on both sides. The word “cartels” is often used—“mafia” is sometimes another common term for these pervasive gangs. Criminals are in love with euphemism. Piedra (stone) is the word for crack cocaine, marimba and mota for marijuana, and agua de chango —“monkey water”—for a liquid heroin-mixture high. Montado is Spanish for being mounted, as on a horse; but it is the border word for an innocent person subjected to torture.

A common border word (I often heard it) is gabacho, which most Spanish speakers would recognize as “frog,” the usual slur for a French person; but on the border—and it has traveled deeper into Mexico—gabacho is an insulting word for a gringo. Coyote, seldom used to describe an animal, is a human smuggler or trafficker at the Mexico-U.S. border.

“Be careful, those kids are halcones,” I was advised on a back street in Nuevo Laredo. This word for falcons is the border term for lookout or spy, and many have an Artful Dodger jauntiness.

**********

The border is not the simple line it seems: it has altered greatly over the past 170-odd years. The United States has expanded through conquest; Mexico has contracted in defeat; indigenous people have been displaced. Much of what is now our West and Southwest was once Mexican territory.

“Mexico—Alta California—extended from the Pacific to the east, and would have included what we now know as Utah, Nevada and Arizona,” says Pulitzer Prize-winning historian Steven Hahn, author of the forthcoming A Nation Without Borders: The United States and Its World in an Age of Civil Wars, 1830-1910.

But that northern one-third of old Mexico was ceded to the United States after the Mexican-American War (1846-48), provoked in 1845 by the U.S. annexation of Texas. California at that time was still sparsely settled, just a chain of missions on El Camino Real of the Mexican province of Alta California, from San Diego to San Francisco Bay.

In 1848, the Treaty of Guadalupe Hidalgo established the Rio Grande as the southern border of Texas. Arizona, once part of the territory of New Mexico, did not become a state until 1912, but the straight line of its southern border was defined by the Gadsden Purchase (1854)—a region inconvenient and hard to police, across stony hill and dusty dale, in the desert.

Throughout the border disputes, among the colonials and newcomers, the Native Americans—who had occupied this region for hundreds of years —were regarded as a nuisance. They were brutalized for objecting to the interlopers and for asserting ancestral claims to their home. The Apaches (to use the popular term for a collection of nations) were particularly tenacious; they were seen as war-like, and slaughtered.

The descendants of all these native peoples remain, and following the border today one encounters the reservations and tribal lands of indigenous folk, from the Cabazon people near Coachella, California, and the Ewiiiaapaayp Band of Kumeyaay Indians (also known as the Cuyapaipe) near San Diego, to the Cocopah at the Arizona state line, the Tohono O’odham farther east, the Mescalero Apache in southern New Mexico, and in Texas the Ysleta del Sur Pueblo near El Paso and the Kickapoo people in Eagle Pass. Among other things, the borderland is a living repository of native peoples.

The border we know today was established as an international frontier from about the middle of the 19th century. For more than 100 years, from before 1900, Mexicans were encouraged by U.S. farmers to cross the border to work in the fields. These men and women were a primary source of agricultural labor in the Southwest and California. To regulate the flow of fieldworkers, the Bracero Program (Mexicans working on short-term contracts) was established in 1942 under an agreement between the U.S. and Mexico. After 22 years, and 4.6 million braceros, the program ended in 1964, the remaining braceros sent home. The American need for cheap labor has defined the border culture.

Once, the border had been porous, and in many places informal and notional, people strolling across in both directions, to work, to shop, to find entertainment, and to settle. Mormons fled south across the border to escape U.S. persecution for their polygamy; Mexicans headed north for work. The border itself was relatively harmonious. Many people I met spoke of mutual cooperation between border towns—the Nogales, Arizona, fire brigade dousing a fire in Nogales, Mexico, and vice versa.

In 1994 the Clinton administration activated Operation Gatekeeper, and thereafter the border became characterized by high fences, patrol cars, security technology and massive deportations of illegal border crossers. Crime, the drug trade, human trafficking, cartel violence, and fears raised by the bombing of the World Trade Center in 1993 created the need to tighten the borders further. And that is where we are today, the border a front line in what sometimes seems a war, at other times an endless game of cat and mouse.

As for the reactions to Mexicans today, Steven Hahn says, “American nativism has a deep and ugly history.”

**********

The border demographic is unlike anything elsewhere in the U.S. “Border cities are immigrant cities,” a man told me on my travels. “Populated by people from all over. You can talk to anyone.” From San Ysidro in the west (across from Tijuana), to Brownsville in the east (across from Matamoros), the spillover means that a non-Spanish-speaking American is at a distinct disadvantage in shopping, buying gas, and eating in many U.S. restaurants, and fraternizing with many workers.

“That isn’t really Mexico over there,” I often heard. But the cultural mix occurs on the American side, too, much of which is saturated with the jolly vida Mexicana, as well as the odious narco cultura.

“We used to go across all the time,” was a common refrain I heard on the U.S. side, usually by a laughing older man; and then I would sit through a sordid reminiscence of his less rational youth in a Boys Town bar.

But the old U.S. habit of crossing the border to carouse is over. The souvenir shops are empty, and so are the bars. Sombreros and ceramic skulls and beads sit unsold and unremarked upon. During the day the Mexican towns are tranquil enough; after dark, not so much. There may be a curfew that is strictly enforced by the police or the army (“Who take no prisoners,” a man told me in Nuevo Laredo). And for all the downtown serenity—the lollygagging and churchgoing, the taco stands and the mariachi bands, and the shoe-shiners in the plaza—one is urged by locals to avoid venturing out of town, even to the nearer country areas, where the cartel gangsters are holed up, and well-armed, and predatory.

“They will take your watch, your car,” a man told me in a whisper in Ciudad Miguel Alemán, across from the Texas town of Roma. Uttering the name of a cartel, the speakers always became breathless with fear. “Your life, señor.”

Roma is a fossilized 19th-century trading town, still with some attractive but abandoned old buildings—handmade bricks, ornate cornices, iron balconies. Like many once-elegant U.S. border towns—Del Rio, Eagle Pass, Douglas and others—Roma barely existed, looked neglected, underfunded and overlooked. But its sister city, Ciudad Miguel Alemán, on the Mexican side (families waved to me from the riverbank), was busy, with a U.S. Coca-Cola factory and an attractive city center.

One of the common denominators I noticed of the Mexican towns was—indisputably—civic pride. The street sweeper and his handcart was a feature of every border town I visited, and the local boast was that life was quite a bit better there than in other border towns—even though a violent drug cartel dominated the place.

This “Our Town” feeling of belonging—the assertion, “I was born in Reynosa, I grew up in Reynosa, this is my home”—gave me hope, because the speaker was a ten-minute walk from McAllen, Texas.

But I should add that McAllen, and its nearer Texan towns of Mission and Hidalgo, are also beset by the incursions of migrants, some from the poorer states deeper in Mexico, but more commonly from El Salvador, Honduras and Guatemala, who have been spirited across the river from Reynosa by the coyotes. Migrants run through the area pursued by U.S. Border Patrol agents, or are held—30 at a time—in “safe houses” until the cartels and human smugglers can move them on.

Most people on either side of the border seem to be reasonably content, going to work and to school, living their lives, saluting their respective flag, voting in local elections, raising children. They are settled, they stay home, they merely fantasize about the country over the fence or across the river.

At the same time, like a rumble on a lower frequency, in an alternate reality, there is a constant skirmishing, the equivalent of a border war, as migrants —desperate, criminal, opportunistic or tragic—attempt to get to the other side, often with the help of human smugglers, usually cartel members, who demand large sums of money from the migrants. And there are more than 20,000 Border Patrol agents who work day and night to thwart them.

Not only men and women try to secure the border, but steel fences as high as 26 feet that run for miles; shorter fences, sections of wall, vehicle barriers, drones, helicopters, bottlenecks at bridges, checkpoints on back roads and on the interstates, sniffer dogs, and over the Texas towns of Zapata and McAllen vast white balloons, the sort that are deployed for antiterrorism in Iraq and Afghanistan—enormous dirigibles used for surveillance, tethered to the border, listening and watching.

And the river, and the desert, and coils of razor wire. The notion of building a wall strikes most people on either side as laughable. The belief is: Show me a 30-foot wall and I will show you a 35-foot ladder. (A survey released in July showed that 72 percent of Americans in border cities, and 86 percent in Mexican-side cities, oppose construction of walls to separate the two countries.)

“I guess some people swim across the river,” I said to a man in San Luis Río Colorado, in Mexico, not far from San Luis, its U.S. counterpart near Yuma, Arizona.

“No swimming,” he said, and giggled and showed his gap-toothed smile. “There’s no water in the river.”

“Then they go over the fence?”

“Abajo,” he said, with a wink. Under it. “Túneles. They travel in tunnels.”

Tunnels, long ones, short ones, high-tech ones, rabbit holes, rat runs, have been dug wherever the border is fenced. One of the longest ever was recently discovered running half a mile under the border, from the bottom of an elevator shaft in a house in Tijuana to a fenced-in lot on the U.S. side. These resemble the mile-long tunnel that led to drug lord El Chapo’s cell in his high-security Mexican prison, and they are built by serious and experienced technicians.

**********

Birds were singing in Border Field State Park near the beach outside San Ysidro, a district of San Diego. There are many pretty birds in the park, and some desperate human fugitives. It was here that I began my journey. You may not see the clapper rail, once close to extinction, but now you’ll hear its clanking call, and glimpse the California least tern and the western snowy plover. Compared with distressed San Ysidro, the houses and villas on the Mexican side in Tijuana on Calle Cascada look imposing on their natural palisade.

I was walking on the sandy path at the margin of the park, at the far western end of the frontier, which is marked by a tall, rust-colored iron fence, paralleling an older, lower fence that ends in the Pacific Ocean. It happened to be low tide that mid-morning—and I was to discover that this detail mattered.

On weekdays, cars are forbidden to enter the park, which is not bosky or park-like at all but a wilderness of sandy scrubland with dense head-high undergrowth, where strollers and bird-watchers are allowed. I was on my own that hot day. The only sound was bird song, and the buzz of two Border Patrol agents on ATVs zipping much too fast past me on the sandy paths.

“They’re looking for someone who just came over because of the low tide,” a ranger told me. I had hailed him in his truck to ask directions. “He’s over there.”

The man had gone to ground somewhere on the northern side of the wetland, near the Tijuana River, hiding in the low bush, within sight of Imperial Beach. The patrols were scouring the area, and a helicopter had now arrived and was hovering.

“If he eludes them until dark,” the ranger said, “he’ll make a run for it in the middle of the night.” Then he smiled. “Years ago I’d see 30 or 40 guys bum-rush the fence, on the assumption that two or three would make it. You don’t see that anymore.”

The miles of hiking in Border Field State Park gave me an appetite. I drove to a parking lot near the entry to Tijuana, and walked across the border and for the first and only time at a Mexican border post, I filled out an immigration form and had my passport stamped. Then I took a taxi to the Avenida Revolución, the heart of Tijuana, and walked to a restaurant, Cenaduria La Once Antojitos Mexicanos, which had been recommended to me for its pozole. Sitting there, bringing my notes up to date, I was happy—well-fed, amazed at the ease of my border crossing, and enlightened by a conversation with a man at the Cenaduria.

“We go to California all the time,” he said. “We buy jeans, shirts, TV sets. A lot of it is made in Mexico. Even with the Mexican duty we have to pay on the way back, it’s cheaper for us.”

This explained the many Mexicans I saw struggling with bundles at border posts all the way to Brownsville. And like most of the Mexican border towns I was to visit, Tijuana was thick with pharmacies, dentists, doctors and cut- price optometrists.

In a routine that served me for the next few weeks, I wandered around the busy, seemingly safe part of the city. As in other border towns, I was welcomed as a harmless older gringo who might buy a sombrero or a leather jacket or a belt buckle bulging with a dead scorpion encased in epoxy.

“What do you think of Donald Trump?” was a frequent question. Predictably, he was not a favorite with Mexicans, whose country he had accused of exporting rapists and murderers. But many employees of the U.S. Customs and Border Protection I engaged on this subject acknowledged they’d vote for him.

Retail business was slow in Tijuana, though the dentists were busy, the pharmacies brisk (Viagra at $5 a pill), and I was assured that the bars would liven up after dark. But people I met said that if I insisted on seeing the border I should do so in daylight. As night fell, I was in a queue of perhaps 400 people, none of them gringos, crowding to leave Mexico.

The next day, driving via Calexico and Mexicali to Yuma, through the desert and the rubbly hills, many of them composed of smooth tumbled boulders, I thought: Who on earth could cross this desert? It was magnificent and parched and inhospitable, much of it Native American land, sand dunes and stony ravines. The evidence that migrants did attempt to cross were the many flagpoles, set a few hundred yards apart, flying striped flags, indicating bins lettered agua, containing plastic gallon jugs of water, for migrants dying of thirst.

Calexico, California, is little more than a crossroads, with the appearance (surrounded by dusty fields) of an oasis; Mexicali a mile away is equally humble in appearance, but boosted by factories—Honeywell, Mitsubishi, Goodrich, Gulfstream and other companies—that relocated over the border to find laborers who would work for $6 a day. (The factories rarely hire anyone younger than 18—but applicants may forge identity papers to get hired.)

Just a few days after leaving Calexico, I read a news item that reported a Border Patrol agent had discovered a 142-foot tunnel just outside the town, “The third such tunnel discovered in Calexico in the past year.”

In that area, and farther east, around Yuma, in the lettuce and broccoli fields, many workers are Mexicans who have been granted federal H-2A visas—temporary agricultural visas—harvesting for farmers who have proven they cannot find American field hands. More than 90,000 such visas are issued every year, allowing Mexicans to work for a few months to a year.

Towns don’t get much poorer than Gadsden or Somerton, Arizona—shacks, rotted trailers, shuttered shops, abandoned houses, baking in the desert sun, hemmed in by the tall rusty border fence. San Luis Rio Colorado, on the other side of the fence (turn right on Urtuzuastegui Street, then proceed over the bridge), is more solidly built, with a park and a cathedral and Plaza Benito Juárez. Four miles up the road is the Bose factory, which employs more than 1,200 people. The next time you clap on your expensive Bose headphones or fire up your car stereo system, consider that they were made by someone living in a hut in the Sonoran Desert, and longing for something better.

It was in that plaza in San Luis that the gap-toothed man smiled and whispered to me, “They travel in tunnels.”

But for me, San Luis was the simplest border crossing of all—a mere stroll, there and back, no lines, no hassle, then back in my car.

Nogales is a 300-mile drive from Yuma, veering away from the border, then back again. In many respects, Nogales is one of the most welcoming border towns—a reasonably good hotel (the Fray Marcos), a wonderful restaurant (La Roca), a folksy bar (the Salon Regis) and enough dentists near Canal Street for it to be renamed Root Canal Street. Four years after I had previously visited, Nogales seemed more upbeat and busier, but one of its institutions was unchanged—except in one respect.

El Comedor—the dining room—run by the Kino Border Initiative, offering humanitarian aid to migrants, was more full of desperate and perplexed people than I had seen previously. The dining facility (and a shelter for women and children) is run by American and Mexican Jesuit priests, the Missionary Sisters of the Eucharist (a Mexican order) and volunteers like my friend Peg Bowden, whose book, A Land of Hard Edges, describes her border experiences.

“Our mission is a humanizing presence,” Father Sean Carroll said to me, as breakfast was served to the migrants. Father Carroll, who had a parish near East Los Angeles, has overseen the Comedor for more than seven years. In the midst of this distress he is energetic, humble and hopeful.

Bienvenidos Migrantes-Deportados y en Transito—the sign reads. The majority of the migrants have been deported over the border; others may be waiting for a chance to push onward. Father Carroll makes no judgments, his organization offers food and clothes (it snowed last winter in Nogales), and a degree of protection from the cartels and the coyotes.

Talking to some of the migrants, I realized that all of them came from southern Mexico—none from the border.

“NAFTA has had an impact,” Father Carroll said. “They export food crops so cheaply into Mexico that the small farmers have been driven out of business. Take a traditional farmer in Chiapas or Oaxaca who grows blue corn. How can he compete with a GMO crop?”

One of the first consequences of the North American Free Trade Agreement, I learned later, was the emigration of the poor from southern Mexico, who had lost their livelihood as farmers and small manufacturers: NAFTA, in effect since 1994, had put them out of business. Some of them ended up in border factories, others as border jumpers.

And here was Letitia, tiny, 22, from the state of Oaxaca, an indigenous Mexican whose first language was Zapotec. Her Spanish was not much better than mine. She’d married two years ago, given birth to a daughter, and her husband, from an impoverished farming family, migrated—without papers—to Florida, where he works in a fertilizer and chemical plant. She had made two attempts to cross the border.

“My agreement with the mafia was that I’d pay $7,000 altogether, first a down payment, and then $4,500 when they got me to Phoenix.”

After three days walking in the desert beyond Sasabe, a popular smuggling point on the Arizona-Mexico border, Letitia was arrested and given two and a half months’ detention—a punitive sentence. She was dazed from her deportation, and conflicted—her husband in Florida, her daughter in Oaxaca. After a period of recovery at the Comedor, she was headed back to Oaxaca.

Norma’s husband, Juan, had worked for 15 years in the fields in Fresno, picking peaches, oranges and grapes; undocumented. Norma worked in a chicken-processing plant there for nine years, but was called back to Mexico by her family in Tehuantepec (2,500 miles from Fresno). “I was so worried I didn’t think about not having papers.” She had made three attempts to cross the border back to the U.S., paying or promising thousands of dollars to the mafia and the coyotes. She was lame from walking in the desert. “I’m going to try again,” she said, and began to cry. Her small daughter was in Fresno.

“Four days ago, I was released from detention,” Teresa told me. She was 48 but looked much older, sad and awkward. Her wish was to work in a hotel in the U.S., “making beds, and cleaning, and another life”—her children were grown, her husband had abandoned her. But the fake ID that someone had given her didn’t work. She was arrested, imprisoned and sent back.

“I’m afraid to be here, because of the mafia,” she told me. And she was right to worry: The cartels and the coyotes prey on migrants.

For ten years, Arturo, 37, worked in a restaurant kitchen in Ventura, California. He was deported after being stopped by a police officer who saw that he was driving erratically. “Five beers,” Arturo said, shaking his head. Trying to return, he had walked for four days in the desert near Puerto Peñasco. “My feet are bad. I had to go to the hospital for medicine. I can’t walk.”

Similar tales from others, though Daneris, who was 16 (and looked 14) from Honduras had a different story: Persecuted by the gangs (maras) in the city of Tegucigalpa, he hopped the train from southern Mexico known as La Bestia, The Beast—18 days riding on the roof of a freight car. He was hoping for political asylum.

And so they huddled in El Comedor, under the benign gaze of Father Sean and his helpers. They prayed, they healed and then they dispersed, some southward to their old homes, others to make another attempt on the border. Judge not lest ye be judged, Father Carroll might have said.

A few hours beyond Nogales, at another crossing at Douglas, Arizona, I met Mark Adams, who strolled with me over the border to the little town of Agua Prieta. “The fence doesn’t define us,” he said. After 18 years on the border heading the Presbyterian organization Frontera de Cristo and its outreach programs (health, education, cultural), he’d seen more similarities on the border than differences. Mark said, “It’s simple really. Do justice, love mercy, walk humbly with God.”

It was Mark’s contention that Mexican immigration is net zero. The growth now was from Central America, people fleeing violence. (There have also been reports of what U.S. authorities call Special Interest Aliens—from African countries, or Pakistan, for example—who crowd immigrant-detention cells in places like Florence, Arizona.)

The following day a concert would be held, Mark told me, half the choir on the Mexican side of the fence, the other half in the U.S., singing together, an event, he said, to promote unity, growth and peace. Perhaps it was working; Douglas (with high unemployment, but quiet) and Agua Prieta (with its 19 factories making everything from Velcro to seat belts and window blinds) stood out as the calmest border towns I saw in the whole of my trip.

On my way to El Paso and Juárez, I talked to Molly Molloy, a Latin American specialist at New Mexico State University Library in Las Cruces. In her scrupulously maintained database of statistics and eyewitness accounts of violence in Juárez, she had concluded that the murder rate rose when, in 2008, some 8,000 Mexican army and federal police were sent to the city. Within days, the murders, the abductions and the lynchings increased, reaching their peak in 2010. “It was a kind of terror,” Molly said. “The murders declined when the troops left.”

Julián Cardona confirmed this in our driving around Juárez, and he showed me a video that was circulating that day, of a woman in Guerrero state being tortured by soldiers, a plastic bag tightened over her head, as she was being interrogated. “Do you remember now?” a torturer in an army uniform kept repeating. Soon after, Mexico’s Secretary of Defense apologized for the criminal aggression of the soldiers.

“This also happened in Juárez—this happens every day in Mexico,” Julián said. And driving through the back streets on the impoverished west side of Juárez, he said that Delphi, Flextronics, Honeywell, Lear and other manufacturers are employers here. Their workers live in these gritty neighborhoods. “About half a million people live here. At one time, there was just one high school.”

It was in Del Rio, Texas, where I found that large numbers of Americans lived over the river in Ciudad Acuña: 20 percent was the figure that Myrta gave me—she crossed to the U.S. every day to make tacos. Once there had been bullfights in Acuña, but the Plaza de Toros had become a market square. Some boarded-up saloons were signposted, “Ladies Bar.”

“Where you could find a lady to take home,” Jesús Ruben explained in his unvisited souvenir shop.

“They make car parts and safety belts there now,” Myrta said. “But workers earn 75 pesos a day ($4.03). I’d rather commute to Del Rio and make tacos.”

I was struck in Ciudad Acuña, and the following days crossing from Eagle Pass to Piedras Negras, and again in Nuevo Laredo, by the sight of families with children on weekend outings —playing in parks, eating ice cream, kicking footballs. The sight of these families gave color and vitality to the towns south of the border.

“In the States, the kids are playing with their Xbox,” said Michael Smith, of the Holding Institute Community Center (promoting adult education and the welfare of the underserved in Laredo). “Over the border, they have no money—so they go on little outings and picnics. The families tend to create their own activities.”

Smith’s colleague Jaime suggested that on my drive east I detour at a town called Rio Bravo, take a side road at El Cenizo and look at the river. I did so and found an idyllic spot, no houses or fences in sight, an easy swim from one side to the other—and a lovely touch that day, the near bank thick with sulphur yellow butterflies, fluttering over the mud like confetti. But also the litter of swimmers who’d made it across: discarded shoes, water bottles, old socks, toothbrushes.

“I crossed there with 20 guys,” a man named German told me later in Matamoros. “We swam and most of us got jobs nearby in Rio Grande City. If we’d gone up the road the Border Patrol would have arrested us at the checkpoints. But we stayed on the border, and after three years I swam back.”

I was nearing the end of the border. At Hidalgo I walked across to Reynosa, which has a terrible reputation for cartels. But Reynosa’s two large hotels on the plaza were inexpensive and pleasant, and I had a good meal at the restaurant La Estrella.

“And on Calle Dama there used to be many chamacas [young girls],” a man named Ponciano told me. “Many gringos used to come here looking for them. Not many these days. Now we make seat belts.”

Schoolchildren hurrying through the streets, in school uniforms, hugging books; old men selecting red peppers and women buying tortilla flour; a youthful population, some of them in identical T-shirts canvassing for votes for their candidate in a coming election; parishioners going in and out of the cathedral on the plaza; and on the back streets and the pedestrian mall people shopping or chatting at taco stands. Nothing could have looked more peaceful.

“I haven’t been there in many years,” the U.S. immigration official told me on my way back, as she matched my passport photo to my face. “I hear it’s like the Wild West over there.”

Some curio shops were selling large piñatas of El Chapo and Bernie Sanders and Donald Trump in Matamoros, but there were no American buyers: The gringos of Brownsville stayed at home, knowing that the cartels control Matamoros. But the criminal activity was nocturnal and cross-border, mainly drugs—crystal meth and “monkey water” and weed; and the transporting of desperate migrants; and the rounding up of girls and women for brothels in Texas and farther north.

I kept my head down, as I’d done since Tijuana, and kept going, down the narrow road to Boca Chica and the Gulf and the last of the frontier. “Turtle Nesting Season,” a sign warned, and over the breaking waves a flock of brown pelicans soaring in formation.

On the sandy beach at Boca Chica families were picnicking and splashing in the waves, and just down the narrow road, Route 4, a Border Patrol checkpoint routinely (“Pretty often,” an officer there told me) finds Mexicans who have swum across the river and are either on foot or hidden in vehicles. Serene vacationers side by side with desperate border jumpers—these, and even greater contradictions, are the everyday of the frontier.

I ended my trip greatly enlightened, and with shinier shoes; and the memory of the border as the front line of a battleground—our tall fences, their long tunnels—and weeping mothers, separated from their children. We want drugs, we depend on cheap labor, and (knowing our weaknesses) the cartels fight to own the border.

I drove back to Laredo and away from the border to San Antonio. It was Fiesta in this happy city, 11 days of music, food, games, parades, hilarity, costumes and nighttime safety. And I thought: No wonder people want to come here.