Governor Jan Brewer talks about the immigration bill
Arizona's governor has signed into law a tough bill aimed to stem the flow of illegal migrants into the US border state.
The BBC's Rajesh Mirchandani travelled to Arizona to test the mood among local residents and also Mexicans who work there.
Nogales, Arizona, is a scruffy hotch-potch of cultures where shops sell cheap T-shirts behind signs saying "Acceptamos pesos" (We accept pesos), where men in trucks drive past blaring Mexican hip-hop and where you'll get a better deal if you haggle in Spanish.
Some families are now separated by the fence
It's a frontier town on a frontline.
Rather than peter out into the desert, the town - and the US nation here - ends abruptly, butted along its southern edge by a 35ft-high (11m) fence, rust-red iron stakes with narrow slits between them, almost taunting those on one side with glimpses of what lies on the other.
And on the other side, clinging to the fence like crumbling concrete moss, is the city of Nogales, Mexico.
You might think this was one city sliced down the middle, were it not for the fact that the Mexican side looks much poorer.
These are two very different worlds, and the fence is the main deterrent in these parts to illegal immigration.
In a state of some 6.5m people, nearly 500,000 are here without permission.
This was one of the last places in America to be homesteaded. There used to be Apaches. It was the Wild West. It's getting like that again
Bill Mcdonald Local resident
Now, with the new anti-immigration law, Arizona has another way to implement its strategy: to make life so hard for illegal immigrants, that they either go home or don't come in the first place.
Police will be required to stop anyone they "reasonably suspect" is here illegally. If that person can't prove legal immigration status they could be arrested.
"It makes me sad," said an older gentleman, a US citizen with Mexican roots, "it will hurt our dignity."
"Search me because my skin is brown?" a young man, also a US citizen, exclaimed. "That's bullshit!"
Two young Mexican women who, like many, often cross the border for a day's shopping, said they might not return to spend their money here in the future.
Several law enforcement officials complain the new measure will increase their workload. Some doubt it will be enforced.
Original Wild West
All the same, most Arizonans support the new law.
And as you leave Nogales and head into the empty desert, opinions change as the landscape does.
Buildings and people give way to spiny cactus plants and desert birds along a quiet highway that winds through beautiful untamed hillsides.
They are unusually green this spring. But soon they will be a parched furnace.
This is the original Wild West, dotted with old mining towns like Bisbee and Tombstone where the actual Gunfight at the OK Corral took place. Now tourists watch daily re-enactments.
The border in this remote corner of Arizona is less heavily fortified than in the cities. Despite the vigilance of the border patrol, it's a busy smuggling route for people and drugs.
And in this dusty remote corner some 25 ranchers work a million acres. They often find human debris on their vast lands, or encounter people trying to cross into America. Most are tired, thirsty and looking for work, but not all.
"This was one of the last places in America to be homesteaded," says Bill Mcdonald, whose family has been here for 100 years.
"There used to be Apaches. It was the Wild West. It's getting like that again," he says.
Taking no chances
Recently a rancher called Robert Krentz was shot dead on his property, along with his dog. Police followed tracks to the border and suspect it was an illegal entrant who killed him.
Rancher Peggy Davis always carries a gun with her
One theory is that it may have been a revenge attack: shortly before, Mr Krentz's brother discovered drugs hidden on their land and alerted police, who removed them.
Now some here take no chances.
On her family's ranch, Peggy Davis plays with her four-year-old grandson Zane and his pet goat Gordy. She tells me now when she goes out, she carries a gun. Peggy supports the new law.
"We have been absolutely overrun," she says, "and our government has not done what they need to to maintain safety I feel this is a national security issue."
Arizona's Governor Jan Brewer, who faces a tough re-election battle this year and who signed the anti-immigration bill live on TV, agrees.
So does President Barack Obama. He said it was the federal government's failure to act that had opened the door to irresponsible measures like the Arizona law.
He wants to reform immigration in the US, and people in border states want him to do it. But they disagree on how.
Back in Nogales, I saw a woman with her four small children huddled by the metal fence. A US border agent watched as a man's hand poked through the iron stakes and caressed the head of one of his daughters. This was a family separated by the fence.
The woman said she was in the US legally, while her husband had failed once before to jump the fence.
Are you worried about the new law, I asked. Will you try and come over again?
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