Arrests of illegal immigrants on the U.S.-Mexico border have fallen to levels unseen since the 1970s as the ailing U.S. economy and enhanced enforcement appear to be deterring people from trekking north.
The trend is apparent from San Diego to Brownsville, Texas, but is most dramatically felt on the border's busiest illegal immigrant corridors, which extend through the Mexican state of Sonora to Arizona and California.
In the sleepy Sonoran town of San Luis Rio Colorado, the migrants that once streamed through have all but disappeared. Piles of donated clothing spill from a closet at the town's migrant shelter, and shoeshine boys now outnumber slumbering immigrants at Benito Juarez Plaza.
Just across the border in Yuma County, Ariz., there are days when U.S. Border Patrol agents don't arrest anyone, an almost unthinkable prospect three years ago when the area was the busiest illegal crossing point into the country, with thousands of immigrants flooding across on some days.
"We were in shock," said Ben Vik, a U.S. Border Patrol spokesman, referring to the two days in December when no apprehensions were reported in the patrol sector that protects 126 miles of the frontier.
From October 2008 through February of this year, the Border Patrol arrested 195,399 illegal immigrants, a 24% decrease from the same period last year. The apprehension level is on track to dip to about 550,000 for this federal fiscal year, the lowest level since 1975, when 596,796 immigrants were caught, according to Border Patrol statistics.
The downward trend in arrests -- considered one of the best indicators of illegal immigrant migration -- began a few years ago, about the same time the federal government started fortifying the border with more agents, fencing and infrastructure.
The border enhancements weren't enough on their own to stop immigrants from entering the country. But with the U.S. economy in a tailspin, few incentives remain for immigrants to endure the increasingly difficult crossings.
"A lot of people who would have come here illegally and stayed illegally are not bothering to come to the U.S.," said Demetrios Papademetriou, president of the Migration Policy Institute, a Washington-based think tank. "The information that they are getting basically says there are no opportunities here."
Many immigrants still try. For them, America's economic troubles seem trifling compared with the meager salaries at home. But the current downward trend breaks with past immigration patterns, when federal crackdowns in one place only led immigration flows to shift to other areas.
Few places illustrate the dramatic turn of events as clearly as San Luis Rio Colorado and its sister communities across the border in Yuma County and the southeastern tip of California.
The region's agricultural fields, lined with rows of lettuce, dates and orange trees, have long provided low-paying but steady work opportunities on both sides of the border. But in recent years the area became a major illegal immigrant corridor for people heading to better-paying jobs in Southern California and beyond.
Immigrants in San Luis Rio Colorado, weary from their border-bound journeys, would sleep in the palm-lined plaza in front of City Hall or cool down inside Immaculate Conception Church.
At night they would sweep across the decrepit border defenses, swarming the trailer parks and cookie-cutter developments of San Luis, Ariz. "They used to knock on my door and run through the yard. My kids were always scared," said Samuel Gonzalez, whose two-bedroom stucco house backs to the border.
In 2006, the area became a symbol of get-tough federal enforcement efforts when President Bush visited to view border improvements, including double-fencing, stadium lighting and enforcement roads.
The sector now has one of the longest stretches of contiguous border fencing in the U.S., including a 13-mile, towering steel barrier that sits atop California's Imperial Sand Dunes. It's also one of the few areas of the border where immigrants caught by the Border Patrol face mandatory jail terms, usually 15 days.
In San Luis Rio Colorado, which has lived with the ebb and flow of immigration since the days of the bracero program decades ago, the situation has brought a sense of relief mixed with loss.
Nerida Rosas, the 74-year-old archivist at Immaculate Conception Church, remembers when the church had to build a soup kitchen for immigrants who would pray under the bell towers and offer to sweep the grounds.
"We had to turn away families sometimes, there were just too many," she said.
Later, floods of immigrants forced the city to open a shelter in a sprawling house seized from drug traffickers. It still wasn't enough; scores of immigrants took refuge in Benito Juarez Plaza, attracting smugglers who would accost anyone young and toting a backpack.
Hoping to restore order, the city last year opened an immigrant aid center, where people could call home, get discounted bus fares home and earn a few pesos by obtaining work permits to wipe down car windshields around town.
But last month, only 45 immigrants visited the center. And many of those, city officials said, were people who had left the United States to return home. "There are hardly any immigrants left anymore. They're scared, and there's no work for them," said Carmen Rios, an assistant in the center.
On a recent day, there were a few reminders of the past.
Sitting in the plaza was a lone group of immigrants -- four men, three women and two teenage boys. One young man said they had been arrested by the Border Patrol and had spent two days in jail before being deported.
They faced a dilemma, he said. There was no work in the cornfields in Guerrero, but they were fearful of facing the towering border barriers and potentially more jail time.
But hadn't they heard about the economic troubles north of the border? The young man didn't answer. Instead he put his hand to his lips and mimicked eating a torta. The others nodded in agreement.
"We're hungry," he said.