The tensions finally spilled over this month with passage of the nation's toughest law against illegal immigration, a measure that has put Arizona at the center of the heated debate over how to deal with the millions of people who sneak into the U.S. every year.
A number of factors combined to produce the law: a heavily conservative Legislature, the ascent of a Republican governor, anger over the federal government's failure to secure the border, and growing anxiety over crime that reached a fever pitch last month with the slaying of an Arizona rancher, apparently by an illegal immigrant.
"It's something that should have been taken care of for years. It's not something we can keep slacking on," said Thomas Fitch, whose neighborhood was the site of a raid last month that netted 11 illegal immigrants in a safe house. "At the rate we're going now, it's going to get a lot worse."
The new law makes it a state crime to be in the U.S. illegally and directs police to question people about their immigration status if there is reason to suspect they are illegal.
Critics warned that the law could result in racial profiling and other abuses, and they are planning a legal challenge and a November referendum to overturn the measure. Supporters of the law say it is a commendable effort to combat what is fast becoming a scourge in the U.S.
Arizona is the biggest gateway into the U.S. for illegal immigrants. The state is home to an estimated 460,000 illegal immigrants - a population larger than that of entire cities such as Cleveland, St. Louis and New Orleans.
The Republican-dominated Legislature has backed a series of tough immigration measures in the past decade, only to have the most aggressive efforts thwarted by then-Gov. Janet Napolitano, a Democrat.
But the political stars aligned this year for the GOP. President Barack Obama appointed Napolitano to his Cabinet, clearing the way for Republican Secretary of State Jan Brewer to take over as governor. The GOP made a headlong rush back into the immigration debate, and Brewer signed the bill last week.
The law reflects frustration with what many lawmakers see as inaction by the federal government.
"While the Bush administration dropped the ball on border security and illegal immigration, the Obama administration can't even find it," said GOP state Rep. John Kavanagh.
He said lawmakers also felt compelled to act because more immigrants will come to the U.S. as the economy improves and there is a "smell of amnesty in the air" under the Obama administration.
Over the past three years, federal agents have made 990,000 arrests of immigrants crossing the border illegally in Arizona, or an average of 900 a day. The figures represent 45 percent of all arrests of illegal immigrants along U.S. borders.
Authorities routinely come across safe houses and vehicles jammed with immigrants across the vast Arizona desert. Last week, 67 illegal immigrants were found crammed inside a U-Haul truck - a fairly typical scenario in the state.
"We're on a hampster wheel here. We're chasing our tail until that border is secured," said Pinal County Sheriff Paul Babea, whose territory includes busy smuggling corridors.
The volume of drugs coming through the Arizona border is also eye-popping. Federal agents seized 1.2 million pounds of marijuana last year in Arizona. That amounts to an average of 1.5 tons per day.
Pot busts have become so common that until recently federal prosecutors in Arizona generally declined to press charges against marijuana smugglers caught with less than 500 pounds.
Phoenix has also been dubbed the kidnapping capital of the U.S. amid a surge of extortion-related abductions tied to drugs and human smuggling. The city has averaged about a kidnapping a day in recent years - some resulting in torture and death. Victims' legs have been burned with irons, their arms have been tied to the ceiling, their fingers broken with bricks.
The anger over immigration-related violence reached a boiling point in late March when a popular cattle rancher named Rob Krentz was gunned down along with his dog on his property near the border. With authorities suspecting an illegal immigrant, politicians seized on the killing to argue that border security is dangerously weak.
There has long been strong public support in Arizona for a crackdown.
In 2004, Arizona voters easily approved a law that denies some welfare benefits to illegal immigrants. It passed with 55 percent of the vote. In 2006, lawmakers put four immigration measures on the ballot, including ones that would deny other government benefits to illegal immigrants and make English the official language. Each measure passed with at least 70 percent.
At the same time, Maricopa County Sheriff Joe Arpaio carved out a reputation as a national leader on illegal immigration, routinely carrying out raids in Hispanic neighborhoods that have prompted a federal investigation. He was elected to a fifth term in 2008.
As the backlash grows over the law, people like Natalia Garcia are closely watching to see how it plays out. She and her husband are illegal immigrants and are afraid that they will get swept up.
"It's taking away our human rights because we have brown skin," she said in Spanish while shopping at a Phoenix grocery store, adding that they will move their family back to Mexico if arrested. "Although we'll live poor, it's better to be together."