The first time I stood on the U.S.-Mexican border in Arizona, I couldn’t believe how inconsequential it felt. I was on a magazine assignment, spending part of a night with a Border Patrol agent. We had been bouncing down an extremely rough dirt road in the Sonoran Desert south of Tucson when he pulled off to the side.

We stepped out into the flat, shadowed light cast by the truck’s headlights, and there it was, the line dividing not just two countries, but the developed and developing worlds, wealth and poverty, philosophical traditions of exceptionalism and fatalism, impatience and old-world courtesy, rock ’n’ roll and mariachi, McDonald’s and taco stands, power lunches and siestas—an endless litany of clichés, true and untrue to varying degrees, but all intended to mark the vast differences between the two nations separated by this border.

Except that, really, there wasn’t much there at all: a modest stone marker and a sagging wire fence, no more than waist high, with only a few loose strands of wire. I dragged my shoe from one country to another, briefly making illegal immigrants of my toes. It felt absurd. Here this little patch of sand was America, here Mexico. Meanwhile, the Sonoran Desert, a landscape as unique and, at night, as haunted as any on earth, stretched in all directions, an overwhelming reality of dark, tangled vegetation and stark landforms thrust unex­pect­edly into the brilliant stars.

The entire night had an absurdist air. The first illegal migrants we came across were crouching politely by the side of a road while a Border Patrol agent moved down the line, lighting their cigarettes for them. (The agents also carry water and crackers; crossing the desert is a thirsty and hungry business.) Migrants would run through the brush until caught and then abruptly give up, a game of tag. Later, we would stop by the Douglas Border Patrol Station where men and women waited phlegmatically to be put aboard buses and sent back to Mexico.

What surprised me most was the courtesy all around, the feeling of people going through a ritual demanded by convention, but so well worn and absent any pressing relevance that the principal requirement to participate was patience. At the time, coyotes—the guides who lead migrants through the desert—often included two or three attempts in their price. The play would go on tomorrow.

That was 10 years ago. I can’t remember exactly where we stopped that night, but if I could find it today, it would be very different. The last time I was in the desert on the border, I stood beside a 14-foot-tall fence made of heavy metal double-mesh that stretched like the spine of an infinite snake across the land, up and down hills, in and out of valleys, and on to the visible end of the world. I was there during the day, but if it had been night, floodlights high on metal poles would have illuminated a space cleared of vegetation on the U.S. side of the fence. Cameras were up there too, and motion detectors were buried in the desert. There were many more Border Patrol agents, and they were more on edge.

Everything has changed along the border. It was already changing at the time of that first visit: more agents, better equipment, increased emphasis on border interdiction as central to immigration policy. All that has continued in an ill-conceived, pell-mell, politically driven throwing of resources at a problem that will feel familiar to anyone who was around during the Vietnam War. But a confluence of events—the deflated U.S. economy and concurrent rise in American nativism, the detonation of the Mexican drug war into a murderous state of low-grade anarchy, and the continued post-9/11 obsession with security in American politics—has changed life here in a way no fence alone could manage.

My family and I have lived in Tucson for a little more than a decade. During that time my work as a freelance writer has repeatedly taken me down to the border, both here and in California. I once came upon a family picnicking on both sides of the fence in San Diego: grand­parents in Mexico reaching through the wire to touch the hands of their grandchildren in America. I spent a day with a church group trooping out into the hot desert to refill the blue water barrels they left along migrant trails, some of which were later stabbed or shot full of holes.

I walked along the fence with a man who can see the border from his front door and whose dog often wanders down to an unfenced riverbed and ends up on the wrong side. He flew an American flag above his house and the whole time we were together packed a pistol on his hip; when he saw Mexicans trudging along their side of the fence, he tossed water bottles to “the poor sons of a bitches.” I’ve talked to an artist who made sculptures out of clothing left behind by migrants near her home, boiling it down to a cloth mache from which she fashioned figures of migrant women. I interviewed a representative of one of the citizens’ groups patrolling the border, a recent legal immigrant herself, with such a strong Teutonic accent I felt immersed in a Saturday Night Live skit.

The border stretches for 1,969 miles, 370 of them in Arizona. It is its own world, a surreal blend of patriotic burlesque and human tragedy, but also part of a larger, shared culture that reaches in both directions. I live in the northern part of that zone, but I hadn’t been across the border to the southern part for a while, so on a bright Saturday morning last fall I joined a small group making a trip to Mexico led by a friend, Joe Wilder, who heads the Southwest Center at the University of Arizona.

The center is dedicated to illuminating the character of the border region, and for years Joe has been taking people across. By midmorning, we were driving slowly through a neighborhood that captured much of the color and flavor of Mexico, the brightly painted buildings with their boldly lettered signs in Spanish, the different rhythm of street life, managing to feel both slower and busier at the same time.

The trip was an introductory tour for Robert Miller, the new director of the university’s school of architecture. At the suggestion of Bob Vint, a Tucson architect guiding the trip with Joe, we followed a battered highway out of the neighborhood—people trudging along the side of the road in the way of developing countries—until we came to a magnificent 18th-century mission church. Standing in front of the whitewashed adobe face, the native village spreading around us, we contemplated the long intermingling of Hispanic and native cultures that gives Mexico so much of its character.

Except we were still an hour from Mexico. The neighborhood we had passed through was in South Tucson, a small city that feels as if it has been transported from below the border. The church is San Xavier del Bac, a National Historic Landmark on the Tohono O’odham Indian Nation, which straddles the border.

It might be a bright line on the map, but the border is blurred on the ground, at least if you measure it as a dividing line between cultures. “Some people think it’s Iowa all the way down to the border, but it’s not,” Wilder observed as we turned toward Mexico. “There are all these other realities that are still alive here. The roots of that indeterminacy go way back.”

The best part of Tucson, where I live, is the result of that indeterminacy. Otherwise, it’s just a sun-blasted place with poisonous creatures crawling about and funny-looking cacti dotting the hillsides. The cultural fusion is woven into life in the city and all of southern Arizona. There are the Sonoran hot dog stands and the mariachi bands. On the weekends before school starts and during the pre-Christmas season, the Sonoran middle class floods Tucson to shop; the parking lots are filled with cars bearing Mexican plates, and English becomes the second language in my local Target store. There’s the huge Day of the Dead parade that probably has more Anglo participants than Latino. There’s a local art scene heavily influenced by Mexican iconography.

But it’s more than that. Tucson has plenty of wealthy people, mostly living in the Foothills section, but this is a poor city overall. More than a fifth of the population lives below the poverty level, nearly twice the national average, and the physical nature of the city is as fine an example of casual Mexican disrepair combined with rapacious American commercialism as you’re likely to find. This feeling of a place with half its history written outside the traditional American narrative exists throughout much of the American Southwest. It may, in part, explain the raging xenophobia that forms a constant subtext in politics here; it can be seen in part as the expression of a deep-seated fear that these places are somehow less American, and as a furious desire to erase that notion.

There’s nothing new, really, about our latest round of immigrant bashing. The United States has alternated between periods of welcoming workers from its southern neighbor and rounding them up and shipping them home. In the 1950s, for instance, “Operation Wetback” included sweeps through barrios and random stops and searches that would warm the hearts of today’s nationalists. Still, the culture along the border has survived, held together by familial, economic, and social ties that transcend the mood swings of American politics.

Despite everything, it was never very hard to cross the U.S.-Mexican border, where there was a culture continuously replenished by an informal, daily social exchange. Border towns shared fire departments and civic clubs. Laredo, Texas, and Nuevo Laredo, Mexico, shared a minor-league baseball team. In some towns, one street was Mexico and the next was the United States; people committed casual acts of illegal immigration to have dinner. Tony Zavaleta, the vice president for external affairs at the University of Texas, Brownsville, can stand on his porch and see a cousin working a farm on the other side of the Rio Grande, in Mexico. When Zavaleta was 14 his grandfather gave him a horse as a gift; he simply had a ranch hand ride it across the river.

Even as the U.S. government began stepping up enforcement along the border in the 1980s and ’90s, this interaction remained vibrant. It survives to this day. Lost in the calls to “secure the border” are the facts that it remains a demarcation between two nations at peace, with strong economic ties and that, as of 2008, it was still the busiest international border in the world, with 220 million legal crossings a year.

America’s talk-show political culture has cost us the ability to see anything except in black and white, but the reality along the border has long been a messy canvas splashed with color. This world has attracted drifters, artists, and opportunists throughout its history, feeding the fluidity of identity. Meanwhile, the monochromatic vision is being imposed by circumstances real and imagined. I’d been down to Mexico many times in the past, and no one I knew had thought much about it, but when I mentioned I was tagging along on this trip, several friends said the same thing, “Be careful.” With Joe Wilder at the wheel of our van, we finally crossed into Mexico at Nogales, Arizona, moving through the gray, modernist U.S. port of entry (in our case, exit) and into the pastel-colored Mexican border station. We were waved through without incident. Even today, nobody much cares if you’re headed into Mexico.

Nogales is also the name of the city below the border. Immediately after we crossed, Joe steered us down the street that runs along the backside of the rusted metal wall, topped with razor wire, that divides the two Nogaleses. We stepped out of the van to get a better look.

The wall is ugly enough on the U.S. side, but on the Mexican side it’s impossible to see it as anything but a physical expression of contempt—shabbily thrown together, made of long strips of corrugated metal that look salvaged from a junkyard. The Mexicans have taken revenge through art. Their side is decorated with murals and metal reliefs created as a testament to the migrants. The most moving are massive collages in which shadows of footsteps are superimposed over photographs of people who died crossing into the United States. You see dozens of faces—old, young, men, women. The power of the photos comes, in part, from their sheer ordinariness; a collection of snapshots of “illegals” turns out to look a lot like a Facebook page—except everybody’s dead.

Nobody knows how many people die trying to cross the border every year. As of late last September, the 2010 tally for Arizona alone stood at 232. But privately, Border Patrol agents will tell you they know they don’t find all the bodies. When people are near death from heat prostration, they usually curl up in whatever shade they can find. Amid the cholla and mesquite, they’re easy to miss. Coyotes and other predators can make short work of the remains.

The fence, of course, is intended to deter illegal crossers. About 650 miles of it now stretch along the border, but there’s no hard evidence that it has had an impact on illegal migration. The most significant factor determining the number of people who try to sneak into the United States is the state of our economy. People come for jobs. When jobs are scarce, fewer people come. Not surprisingly, the number of illegal migrants caught on the border, which is the only real gauge we have of how many people are trying to enter, fell with the advent of the Great Recession.

What the fence has done is displace illegal migration. The Center for Comparative Immigration Studies at the University of California, San Diego, has noted an increase in the number of people trying to cross by water, either along the California Coast or the Gulf of Mexico. Other illegal migrants fly to Canada and enter the United States from the north. The Pew Hispanic Center estimates that 45 percent of illegal immigrants simply cross legally at U.S. ports of entry but don’t leave in accordance with their visas.

For those still trying to make their way into the United States by land, the fence has pushed them into less accessible terrain, country so harsh it forms its own barrier. In doing this, the fence and associated security buildup have probably contributed to the number of people who die trying to cross. To part of the American population, this is not a problem. Suggestions that we should consider shooting or blowing up illegal immigrants (by placing land mines on the border) have been made by elected lawmakers, candidates, radio talk-show hosts, and others in several states.

A surprising number of the immigrants are under the age of 18 and unaccompanied by adults. Not only are they young, they come surprisingly great distances. Enrique’s Journey, written by Los Angeles Times reporter Sonia Nazario, traces the story of a boy from Honduras who made several attempts to make it into the United States, traveling all or part of the 2,000-mile journey again and again until he succeeded. Like many of the children who try to cross the border, Enrique was in search of his mother, who had illegally migrated when he was an infant.

We considered the faces on the mural and then climbed in the van and headed south through Nogales. It was a beautiful, clear-blue day, and the city looked busy, but like other Mexican border towns, its economy is being strangled by drug violence. Two years earlier, when the craziness had begun but hadn’t reached the level it has today, I took my daughter down to Nogales one afternoon to browse among the shops and stalls across the border—the touristy places usually packed by day-trippers. There was almost no one there. In several shops we were the only visitors, and the clerks wore a defeated look. Like everyone I’ve ever spoken to in Nogales, the owner of a shop selling jewelry had family in Arizona—in his case, daughters in Tucson—and he spoke of the state with unabashed affection. But he was desperate for the Americans to return to Nogales. “We are slowly starving here,” he told me.

A few days later a Sonoran policeman stopped a van for a routine inspection and stumbled upon a group of narcos, as the Mexicans call the drug gangs. The running gun battle that raged through town left eight dead and 10 wounded. At one point, the narcos tossed grenades out the windows. I read the story at my dining room table with an eerie focus, trying to determine if they had come near the plaza where my daughter and I sat on a bench and lunched on tacos.

Mexico’s drug war is the great shadow hanging over the southern side of the border. Nogales had at least 131 murders in the first half of 2010, compared with 135 for all of 2009. Three years earlier, it had just 37. This is not the bloody cauldron of Ciudad Juarez, but for a city of about 200,000, the tally is frightening. It’s not just the body count, but also the phantasmagorical nature of the violence: last July two heads were found jammed between the bars of a cemetery fence, an act of terror that has become familiar in Mexican border cities.

Sonorans point out that the violence is focused in certain corridors leading to the United States and maintain that most of the region remains quite safe. This may be true, but as the Mexican government takes on the narcos, the battlefield has a way of shifting. After leaving Nogales we passed a highway leading into the valley of the Rio Altar, an area of villages with picturesque churches, long popular with tourists. As we drove past the highway, it looked closed. A police car idled at the intersection; two officers were inside, dressed in the black uniforms of the Federal Police.

The Altar Valley extends into Arizona, forming a natural human and drug-smuggling route. The Sinaloa cartel and the Beltran Leyva cartel have been fighting over it. Last July a gun battle erupted on a road between the villages of Tubutama and Saric. The shootout left 21 dead and six wounded. Authorities found hundreds of shell casings and eight shot-up SUVs abandoned at the site. Basic commerce in and out of some villages has been blocked, and residents have become hostages in their own homes. Others have fled. The response of the Mexican government is unclear, although it seems to have essentially quarantined the Altar, waiting for the battle to sort itself out.

This lurid backdrop has helped make popular such measures as Arizona’s new law SB1070, which gives police the right to demand proof of citizenship. But despite the ramblings of Governor Jan Brewer about “beheaded” bodies in the desert (the medical examiners of six Arizona counties could not think of a single case), the violence so far has largely stopped at the border. At the height of pre-election hysteria last fall, The Arizona Republic, the state’s largest newspaper, found the rate of violent crimes in Arizona border counties to be down or flat.

America, compared with Mexico, has paid a small price for the drug war, but the toll has been taken in the basic social and cultural commerce along the border. For 35 years, the Southwest Mission Research Center in Tucson had been running tours down to Sonora. The nonprofit center wanted North Americans to appreciate the historic connections between north and south and to see the Mexico beyond the tourist resorts. Altar Valley was one of its popular destinations. Last fall the center suspended operations. “Nobody wants to sign up for the tours,” says Nick Bleser, who with his wife, Birdie Stabel, has been leading trips south since 1978. “Who the hell wants to go down there and get shot?”

There is the wall, and then there is the psychological wall being erected between the two countries. Drug violence is one part of that wall. Arizona SB1070 is another. On one level, it seems to have made little difference. Tucson is still a popular shopping destination for the Mexican middle class. You still see a line of Mexicans at the U.S. port of entry waiting to visit Nogales, Arizona. But the law has frayed longstanding bonds between the Mexican state of Sonora and Arizona. For 50 years, the Arizona-Mexico Commission has met to discuss cross-border cooperation, but after passage of SB1070, the Sonoran government canceled the meeting to protest the new law. The Mexican government has issued an alert to citizens traveling in Arizona, warning that they could be required to prove they are in the country legally at any time.

Many Sonorans feel a sense of betrayal at their treatment by a state to which they have deep connections. Francisco Javier Manzo, a notary public in the Sonoran town of Sonoyta, traces his family’s history in the region back roughly 250 years. His grandfather, a general in the Mexican revolution, lived in Tucson in the 1930s, and he still has friends and family on both sides of the border. “People are being harassed without any reason. Friends of mine have been bothered. They say they will never go back,” he says.

If SB1070 was intended to scare immigrants back into Mexico, there is anecdotal evidence it may be having some effect. Seminario Niñez Migrante, a Sonora-based organization, tracks Mexican families that have returned to the region from the United States. The public schools in Sonora, says the organization’s director, Gloria Ciria Valdéz, have registered 8,000 new students in the last three years, many who were born in the United States and know little or no Spanish. “We have been interviewing the families,” she says, “and they say they are returning for two basic reasons. The first is the economic crisis in the United States, and the second is SB1070.”

For much of the American population, this would be nothing but good news. But for those who care about the shared culture of the border, it carries the weight of sorrow. “What’s being lost is the realization that we have more in common than differences,” Bleser says. “What’s being lost is our sense of this heritage.” Manzo sees history being erased. “There is a long relationship between us and Arizona,” he says. “We cannot live in the global world like this. We need each other.”

Hordes of migrants marching through the night to steal your job, Minutemen and other self-proclaimed patriots playing cowboys and Mexicans in the desert, a state law that gives the police the right to demand your papers, drug-war shootouts in Nogales and other Mexican border towns, beheadings. The media-refracted view of Arizona and its neighbor to the south is cartoonish: a quasi-fascist police state perched above a failing narco state.

It’s as reductionist as any headline scrolling across the screen. Yet the elements out of which it’s constructed are just real enough to obscure other visions of life along the border. Compared to the dead along the migrant trail, the dead in the Mexican drug war, this is a lesser tragedy, but a tragedy nonetheless.

Joe Wilder, the architects, and I drove from Nogales to Magdalena de Kino for lunch. The town is bright and cheerful, with a modern square that holds the tomb of Spanish explorer and missionary Father Kino. There you can look through glass at the bones of a man who 300 years ago was notable for his treatment of the native population and for trying to fuse unlike cultures through charity rather than intimidation.

From there we drove on to the village of San Ignacio, where there’s a handsome, although sadly dilapidated, Kino mission. The highway bent through steep, tangled mountain slopes, country that appeared wilder, greener than around Tucson—familiar yet foreign. I had the sense of seeing this peculiar part of the continent where I live for the first time, and the land, as it always does for me in Mexico, began to take on a feeling of uncomplicated beauty.

We parked on the San Ignacio square with the sun low in the sky. An octagonal bandbox stood in the center of the square, and a solitary man sat on one of the benches, a dog at his feet. Joe left to get a key to the church, while the rest of us wandered back to view it from across the square. In the falling light the whitewashed adobe had the soft, slightly blurred perfection of a bar of Ivory soap. It looked like a long-lost cousin of San Xavier del Bac, and the familiarity filled the air with the threads of history.

Joe returned to say the church had been declared unsafe and we couldn’t go inside. Instead, we went to the home of friends of Joe’s, the Sanchezes, and ended up around the table in their narrow living room while they treated us to quesadillas, and then tamales, and then persimmons. Family members kept appearing, being introduced, and standing politely for a minute or two to talk. Only Joe and Bob spoke enough Spanish to really converse, but language wasn’t much of a barrier. We learned that the priest shut down the church after a piece of plaster landed on his head during Mass.

Casimiro Sanchez makes his living from an orchard on the edge of town. He took us out there in the twilight and we wandered through an unkempt, overgrown Eden while he fussed about. The way he tilted his cap and considered his fruit trees and other plants reminded me of the farmers I grew up around in North Dakota. One of us, it might have been Robert, asked him about the impact of the drug war. “You can live peaceful here if you don’t get tangled up in things,” Casimiro answered, which seemed a rule for life in general, not just in Mexico.

We had a long trip ahead of us to get back to the border crossing, a drive that would end in a line of vehicles creeping toward the surgically lit port of entry. Over an hour’s wait left us dealing with a deadly serious Border Patrol agent who would inspect our passports carefully before letting us reenter the United States. As it happened, we got off lucky. The last couple of times Joe had taken a group across the border, they’d been taken aside and kept for more than an hour in a windowless room while being checked out.

After entering the United States we would have to stop again at one of the floodlit checkpoints set up on the major highways. All day we had been in Mexico, a country in the middle of a murderous conflict, and nothing even vaguely threatening had happened to us. The country that felt the most like a police state was the one we had returned to.

But all that was ahead of us. Earlier, in the Sanchez orchard, lingering with Casimiro, we settled into a more amiable reality, our last few minutes together. No, that didn’t make less serious the drug war, the migrants out in the desert, the legitimate questions of policy that people grapple with concerning the border. But its value was no less for that. The inescapable truth that it has been made much harder for Americans and Mexicans to enjoy these simple moments is something to mourn.

The sun had set and it was quickly getting dark. We dropped Casimiro off at home and drove up a rural highway, making our way back toward the United States until we came upon a string of pickup trucks moving slowly, their beds filled with people, blocking our way.

There was no oncoming traffic, and soon Joe pulled into the right lane to pass. We drove past truck after truck, and then came to men riding horses, children riding bicycles, floats being towed by ancient tractors—girls dressed as Indian princesses, a band blaring away—and then more trucks, horses, children, a parade headed somewhere down a narrow Mexican road in the twilight.

“How ya doin’?” someone in the back of a pickup yelled in an imitation American accent as we passed, and there was laughter, friendly, teasing, slightly giddy. We laughed, too, and pulled past. What was going on? We would never know. It was getting dark and we were heading home, the only Americans on the road.