Arizona is at the centre of the US debate over immigration after introducing a tough new law targeting illegal entrants to the country. The BBC's Robin Lustig travelled to the state's border with Mexico, and met those on the frontline of the issue.
If you look through the bars of the steel fence in Nogales, southern Arizona, you find yourself looking at Nogales, Mexico.
The fence marks the international border between the US and Mexico - and it runs right through the town.
Hundreds of thousands of Mexicans cross this border illegally every year, and an increasing number of Americans want to stop them.
Dealing with illegal immigrants is what Border Patrol Agent Richard Funke does every day.
As he drove me along the high steel border fence, he told me: "You see people watching that fence every hour of every day. Someone tries to get across every day of the year."
And sure enough, within minutes, we had spotted a young Mexican darting through a hole in the fence. But other agents had spotted him too; and he was soon back in Mexico again.
Out in the desert, Agent Funke suddenly pulled over to show me a trail leading from the road towards the border.
"Look at those footprints," he said. "They're no more than a few hours old … someone was here earlier this morning, probably dropping off a consignment of drugs from across the border."
Thirty miles north of the border, I met Pat King, round-faced and friendly, at home on the ranch that she runs with her husband John.
With her grand-daughters scampering about as the sun set below the hills and the shadows lengthened, she told me why she wants illegal immigrants stopped.
"They come across the ranch, right up by the house. Our fences are damaged, our gates are left open, the cattle stray.
"We see so much drug-smuggling, the Mexican cartels are getting much stronger. If the men go out and stumble across a group of smugglers, they're convinced they're going to end up with a bullet in the back."
The Kings' ranch is used as a local headquarters by a group called the Minutemen.
They go out searching for illegal immigrants - and call in the Border Patrol if they find any.
Their local leader, Mike Vyne, a Vietnam veteran, says politicians want to encourage illegal immigrants because they keep labour costs low.
He has little time for Washington, or for President Barack Obama.
"I reckon Obama is in favour of illegal immigrants because they're the only ones who'll vote for him at the next election," he told me.
"That's why he keeps the Border Patrol purposely under-staffed, under-funded, and under-equipped."
'Not at war'
In the rapidly growing town of Casa Grande, baking in the afternoon sun, I met no-nonsense sheriff Paul Babeu. He's an ex-cop and he wants to hunt down every illegal immigrant he can find.
"We're not at war with Mexico," he says. "But there's a clear link between high crime rates and illegal immigrants.
"This new law is a good tool to send out a clear message: 'If you're here illegally, guess what, you're going to be arrested.'"
There are thought to be half a million illegal immigrants in Arizona. If Sheriff Babeu is right, that means his men are going to be making a lot of arrests.
Robin Lustig presents the BBC's The World Tonight.