NOGALES, Ariz. – It’s easy to walk south from the U.S. into Mexico. What’s hard is going the other way.

A team of NPR journalists experienced that for ourselves, on a bright day in March when we passed easily through a legal port of entry that separates Nogales, Arizona, from Nogales, Sonora.

We walked alongside trucks carrying goods between the two countries. This border is a boon for businesses on both sides, recently making Mexico the United States’ biggest trading partner. But it’s also been the source of a major political headache: the arrival of millions of migrants from across the Americas and elsewhere in the world seeking to enter the U.S.

We came here to glimpse a small part of the border on a typical day.

We entered Mexico through a quiet pedestrian access point at the Nogales port of entry, and continued about 100 yards to a shelter where dozens of migrants waited with hopes of crossing la frontera – the U.S. border, marked with large green highway signs.

Children played on a concrete floor at the entrance to the Kino Border Initiative. It was lunchtime, and volunteers milled among long tables, offering drink refills and tortillas to families bundled up in fleeces and jackets.

We met the nonprofit’s executive director, Joanna Williams, in the dining area. On the left side of the room are migrants who have been in Nogales a few days or less, she explained; on the right are travelers stuck in limbo.

“We have some people who have been here for months,” Williams said.

The flow of asylum seekers from around the world has overwhelmed the U.S. government’s capacity to hear their cases. Multiple presidents have addressed the problem in different ways. In 2019, President Trump’s administration told asylum seekers to remain in Mexico, waiting south of the border for U.S. court hearings to determine their status.

Presidents Trump and Biden both used emergency powers during the pandemic to turn away many asylum seekers. Now that those powers have expired, Biden’s administration has urged some people to apply for asylum from their home countries—and urged overland migrants to apply for entry by making appointments on CBP One, a U.S. government phone app.

Today hundreds, even thousands, of people reach this part of the border on a daily basis, but U.S. Customs and Border Protection conducts only 100 asylum interviews per day in Nogales, Williams said.

“They have to apply for an appointment every single day,” Williams said. “It takes the families about five or six months for that request to be granted – unless they win the [interview] lottery.”

A couple seated at a nearby table had just won that lottery, securing an interview with Customs and Border Protection in Nogales. Carla and Jose, who traveled from Venezuela with their two children, were instructed to show up at the port of entry to speak with agents about their case. (NPR agreed to only use Carla and Jose’s first namesto maintain their privacy during the asylum process.)

Carla and Jose hoped the CPB interview would mark the end of a dangerous and costly journey they made by bus, foot and train through at least seven countries.

They made the trek with a family they were related to by marriage – a couple and their 10-year-old daughter – after they heard it would be safer to travel in a group through treacherous jungle in Colombia and Panama. Along the way, Carla said, authorities extorted them on both sides of the border between Guatemala and Mexico, demanding fees up to $200 per person.

Still, it was worth the risk and expense, said Nohelis, a woman whose family had traveled alongside Carla and Jose.

“In Venezuela it’s difficult for us to find food and well-being, especially for the kids,” Nohelis said. “We have to be allied with the government. If you’re not aligned with one of them, you don’t get certain benefits.”

Everyone in the group said they had family living in the U.S. already — in Carla’s case, an adult daughter in Florida. Her family hoped to go there next,after their appointment with Customs and Border Protection, which was scheduled for 2:30 p.m. the following day.

The family agreed that if they were admitted to the U.S., we would meet again there.

Our team started back along the road north. We bought a pink frozen paleta, a popsicle, from a man pushing a cart on a busy road. As we approached the Nogales port of entry, officers with U.S. Customs and Border Protection asked us if we were U.S. citizens. When we said we were, they waved us through without asking to see identification.

U.S. Border Patrol

Carla and Jose represent a challenge for the U.S. Department of Homeland Security because their story is repeated so many times. To get an overview, we visited the regional headquarters of one of the relevant DHS agencies — the U.S. Border Patrol, the law enforcement body that operates under Customs and Border Protection.

John Modlin, the sector’s chief patrol agent, arrived at a conference room prepared with statistics.

In this sector of the border, agents apprehended about 60,000 migrants in the 2019 fiscal year, most of them from Mexico, Modlin said. That was a lot, but manageable, he added.

That number tripled in 2021, and sextupled in 2023, according to federal data.

“If we continue at this rate, we’ll probably hit 700,000, maybe 800,000 apprehensions in the Tucson sector this year,” Modlin said.

For every migrant that used to arrive in the Tucson area, six now come, from Mexico and around the world. They’re pushed and pulled by political upheaval, violence, economics, and shifts in U.S. policy — both real and perceived.

Many who cross the border tell agents that President Donald Trump’s departure from office encouraged them to think the U.S. would be more open, Modlin said.

Meanwhile, cartels in Mexico expanded their human trafficking business across the world, appealing to would-be asylum seekers on social media, Modlin said. Their marketing campaign has lured many more thousands of migrants from troubled countries all over the world, many drawn by hopes of receiving asylum protections.

“What we have seen is a tremendous increase in the amount of people that are claiming fear,” Modlin said. “When this was 85%, 90% Mexican nationals, our ‘total fear’ numbers were probably 1% or 2% across the entire sector. Now, 95% of the in-custody populations are claiming fear.”

Migrants are human chattel for Mexico’s drug cartels, Modlin said.

Guides who work for the cartels offer to lead entire families across the border through the desert. Many vulnerable travelers are dropped off in remote stretches of hostile land, left for patrollers to discover.

“[The cartels] recognize that when they send these groups over, and those groups are in distress, we respond to it, but it will take hours for us to get to where they’re at,” Modlin said. “It’s all very well thought-out by the people on the south side, who have no regard for life. They’ve already been paid. To them, whether that person makes it or dies in the desert, they don’t care.”

Last year, so much of the border force was busy processing migrants, CPB had to close a regular border crossing for lack of personnel.

Modlin said processing has also taken away from the agency’s mission to combat drug trafficking through remote areas, though federal data show that most narcotics are seized at official ports of entry, not between them.

More than 340,000 migrants have arrived in the Tucson sector since November 2023. Those admitted through the CBP One app will be able to work legally in the U.S. while they wait for months – possibly years – for hearings in backlogged immigration courts.

Last winter, Congress drafted a far-reaching immigration plan that included hiring more border agents. The measure failed after Presidential candidate Trump instructed Republicans to block their own bill, so he could campaign on the issue. This spring, Congress slipped in new funding as part of an overall budget plan, though the challenge remains as immense as the Arizona desert.

Hostile terrain

The land along Highway 286 is dotted with wooden crosses, marking the locations where migrants have died.

Kirk Astroth pointed them out to us as we trundled south toward the border in a truck equipped with a giant water tank.

“We’re going off-road here,” announced Astroth, a volunteer with the migrant aid group Humane Borders. He veered onto a rocky path lined with thorny mesquite that scratched the doors and windows of his truck. The long scrapes left behind have a nickname: Arizona pinstripes.

The truck is thoroughly pinstriped after many trips like this. Astroth pulled over to refill a blue water barrel decorated with a sticker of the Virgin Mary.

“We always take a water test first,” Astroth said, sampling a few drops from the barrel. He grimaced. “Tastes like chlorine. But it’s better than dying.”

Authorities found the remains of more than 3,300 migrants in Southern Arizona between 1990 and 2020, according to the Pima County Medical Examiner. Many migrants choose to travel through the desert to avoid a long wait at an official port of entry, even though the government says that will count against them in their eventual asylum hearings. Humane Borders is one of several humanitarian groups that leaves water along commonly used routes.

Sometimes people vandalize the water stations, Astroth said. Over the years, he’s encountered U.S. citizens in the desert who consider themselves unofficial border security.

“They shoot our barrels. They stab the barrels with screwdrivers. They put pen knives in them, throw them – sometimes they just kick the spigots off,” Astroth said. On more than one occasion, armed men in the desert have told Astroth that humanitarian volunteers like him are “no better than getaway car drivers at a bank robbery,” aiding and abetting illegal immigrants, he said.

“We’re not trying to help people elude anything,” Astroth said. “We’re just trying to prevent people from dying.”

Humane Borders does not publish maps showing its water stations – that would give vandals a shortcut, Astroth said. But the group does publish maps showing where migrants have died in the desert.

So far in 2024, the Arizona OpenGIS Initiative for Deceased Migrants has added 32 newly discovered remains to its database. The list is likely to grow as summer heat sets in.

Waiting for a day in court

As we drove around southern Arizona, NPR producer Lilly Quiroz called Carla and Jose, the Venezuelan couple we met the previous day in Mexico. They said they were in line, awaiting their appointment with U.S. Customs and Border Protection. Later, they told us their family had made it through.

They said they caught a late-night bus to a shelter on the U.S. side – Casa Alitas, run by Catholic Community Services of Southern Arizona. We met them there, where they were standing at the edge of a giant room filled with 400 green cots.

Carla and Jose both were beaming, despite staying awake all night. They said they waited for hours at the border with people from all over the world – Russians, Haitians, Cubans, before they were told they could enter the U.S.. They thanked God.

Then the couple’s day got even better. Carla’s daughter in the U.S. told them she would cover plane tickets to bring the family to her home in Orlando. Jose, sifting through documents in a bag, showed us documents from the federal immigration service.

“You are ordered to appear before an immigration judge…” began the official letter from the U.S. Department of Justice.

The letter provided the address to a federal government office in Orlando, where they are to report for a hearing.

“We’re hoping the judge is graceful, and gives us the opportunity to live in this great country,” Carla said, speaking through an interpreter.

Her family has ample time to prepare. The hearing is scheduled for November 18, 2027.

The audio version of this story was produced by Lilly Quiroz. The digital version was edited by Obed Manuel with help from Alfredo Carbajal.