The migrants walk for days through miles of mesquite scrub, running low on food and sometimes water, paying armed drug thug "guides" and dodging U.S. law enforcement officers along the way. And still they keep coming. The latest figures show that Arizona, which is about to put into effect the nation's toughest immigration law, also is the only border state where illegal crossings are on the rise.
While tightened security and daunting fences in Texas and California have made Arizona a busy crossing corridor for years, migrant smugglers now are finding new ways through the state's treacherous deserts.
Carmen Gonzalez, 27, recalled seven days and six nights of walking with her husband in the desert and being accosted by Mexican thugs with AK-47s, who demanded $100 bribes before abandoning them.
"It was so hard and so ugly," Gonzalez said at a shelter in this Mexican border town, where she, her husband and her brother were staying after being deported from Arizona. "I won't try again because we went through too much suffering in the desert."
New U.S. Border Patrol statistics show arrests on the Arizona border were up 6 percent -- by about 10,000 -- from October to April, even as apprehension of illegals dropped 9 percent overall. The agency uses arrests to gauge the flow of migrants; there are no precise figures on the number of illegal crossings.
Statistics from the Mexican side also show a rise in illegal crossings through Arizona.
Grupo Beta, a Mexican government-sponsored group that aids migrants, helped 5,279 people from January to April in the area across the border from Douglas, Ariz., compared to 3,767 in the same period last year, said agent Carlos Oasaya.
That's the same area where Arizona rancher Robert Krentz was fatally shot in March as he surveyed his property in an all-terrain vehicle. Authorities suspect an illegal immigrant who was headed back to Mexico and worked as a scout for drug smugglers.
The killing helped fuel the emotion around the Arizona law, which will empower police to question and arrest anyone they suspect is in the country illegally. It takes effect in July.
Immigration is likely to be at the top of the agenda Wednesday when Mexican President Felipe Calderon visits Washington and attends a state dinner at the White House. Calderon has condemned Arizona's law; President Barack Obama has called it "misguided" and promised to begin tackling an immigration overhaul.
Supporters of the Arizona law said Tuesday that the growth in arrests at the border didn't spur its passing.
Instead, it was a series of factors, including the discovery of a growing numbers of immigrant safe houses and a rise in crime by illegal immigrants who have injured and killed police officers, said state Rep. John Kavanagh.
In the 1990s, increased enforcement and corrugated metal and chain-link fences dramatically cut illegal border crossings in California and Texas.
Overall, illegal immigration through those two states, New Mexico and Arizona has declined from nearly 1.2 million in 2005 to 541,000 last year, according to the Border Patrol. In Arizona, illegal crossings fell from 578,000 in 2005 to nearly 250,000 last year -- before the recent rise.
Immigration experts have long predicted the decline in crossings would reverse as the U.S. economy recovers.
"The fact is that as long as there remains an economic disparity between the U.S. and Mexico and other Latin American countries, enforcement and sanctions and any other measure won't stop the flow of migrants," said Charles Pope, interim director of the Trans-Border Institute at the University of San Diego.
Despite the recent spike in illegal crossings into Arizona, entering the state illegally is getting tougher.
U.S. Border Patrol drones scan for drug and migrant smugglers in the desert. Twelve-foot steel walls now separate the crossings through Nogales, south of Tucson, and Agua Prieta across from Douglas.
The desert around the hamlet of Sasabe, a smuggling way-station of a few dozen houses, is a drug trafficking corridor used by the Sinaloa cartel. Migrants and Mexican officials say heavily armed drug traffickers have been demanding fees since at least 2007 to allow migrants to pass.
Gonzalo Altamirano, a 19-year-old mechanic from the southern Mexican state of Oaxaca, jumped over a fence into Arizona from Agua Prieta. He surrendered to authorities after waiting two days for a van that never arrived.
It was Altamirano's second time crossing illegally into the United States -- he lived and worked in Oklahoma for nine months in 2007 before getting so homesick he returned to Mexico. He intends to try again.
"I'm poor and will always look for a way to cross," he said. "Even if they add more security or whatever."