Once, the barren mesas and shrub-covered canyons that extend east of the Pacific Ocean held the most popular routes for illegal immigrants heading into the U.S. Dozens at a time sprinted to waiting cars or a trolley stop in San Diego, passing border agents who were too busy herding others to pause.
Now, 20 years after that onslaught, crossing would mean scaling two fences, passing a phalanx of agents and eluding cameras positioned to capture every incursion.
The difference, Homeland Security Secretary Janet Napolitano said on a recent tour, is like "a rocket ship and a horse and buggy."
In pure numbers it is this: Where border agents made some 530,000 arrests in San Diego in fiscal year 1993, they had fewer than 30,000 in 2012.
There is no simple yardstick to measure border security. And yet, as the debate over immigration reform ramps back up, many will try.
"Secure the border first" has become not just a popular mantra whenever talk turns to reform but a litmus test for many upon which a broader overhaul is contingent.
In fact, the 1,954-mile border with Mexico is more difficult to breach than ever. Two decades ago, fewer than 4,000 Border Patrol agents manned the entire Southwest border. Today there are 18,500. Some 651 miles of fence have been built, most of that since 2005.
Apprehensions, meanwhile, have plummeted to levels not seen since the early 1970s. But in communities along the international boundary, "secure" means different things.
The tide turned when the U.S. government launched "Operation Gatekeeper" in 1994, modeled on a crackdown the previous year in El Paso. The effort brought 1,000 additional agents to San Diego.
As apprehensions fell, home values skyrocketed. In 2001, an outlet mall opened right along the border. It now counts Brooks Brothers, Polo Ralph Lauren and Coach as tenants.
More than manpower helped to shut down the path into San Diego. An 18-foot-high steel mesh fence extending roughly 14 miles from the Pacific Ocean was completed in 2009, with razor wire topping about half of it. A dirt road traversing an area known as "Smugglers Gulch," which border agents had to navigate slowly, was transformed into a flatter, all-weather artery at a cost of $57 million.
This past year the Border Patrol's San Diego sector made fewer arrests than in any year since 1968.
The question of border security hits close to home to those who work the land in Southern Arizona. It was here, in 2010, that cattle rancher Robert Krentz was gunned down on his property near Douglas. Local authorities have said they believe the killer was involved in smuggling.
That same year, Border Patrol agent Brian Terry was killed in a shootout near Nogales with Mexican gunmen that brought attention to the federal government's botched weapons-trafficking probe called "Fast and Furious."
Defining "secure border" in Arizona is never easy. Just last week, U.S. Sen. John McCain hosted town hall meetings on immigration reform in his home state, and was left defending a plan he's been developing.
The crackdowns in Texas and California in the 1990s have turned Arizona's border into the busiest for human smuggling for 15 years running now.
In 2000, agents in the Tucson Sector made more than 616,000 apprehensions - a near all-time high for any Border Patrol sector. The number eventually began dipping as the agency hired more than 1,000 new agents and the economy collapsed. State crackdowns such as the "show me your papers" law - requiring police enforcing other laws to question the immigration status of those they suspect are in the country illegally - are also thought to have driven migrants away. The result: the sector had 120,000 apprehensions in fiscal 2012.
But the amount of drugs seized in Arizona has soared at the same time. Agents confiscated more than 1 million pounds of marijuana in the Tucson Sector last year, more than double the amount seized in 2005.
In Nogales, Santa Cruz County Sheriff Tony Estrada has a unique perspective. Born in Nogales, Sonora, Mexico, Estrada grew up in Nogales, Ariz., after migrating to the U.S. with his parents. He has served as a lawman in the community since 1966.
He blames border security issues not only on the cartels but on the American demand for drugs. Until that wanes, he said, nothing will change.
"The drugs are going to keep coming. The people are going to keep coming. The only thing you can do is contain it as much as possible," he said. "I say the border is as safe and secure as it can be, but I think people are asking for us to seal the border, and that's unrealistic."
Asked why, he said simply: "That's the nature of the border."
In EL PASO
In the early 1990s, El Paso ran second to San Diego in the number of illegal immigrants coming north. Then, in 1993, the Border Patrol launched "Operation Hold the Line," an enforcement action intended to gain "operational control" of the border.
It was a shift in strategy from apprehending illegal immigrants in the U.S. to preventing entry, and the effect was almost immediate: Within months, illegal crossings in El Paso went from up to 10,000 a day to 500, according to a Government Accountability Office report in 1994.
Burglaries in neighborhoods decreased. Car thefts went down. And, as happened later in San Diego, apprehensions plunged.
in McALLEN, Texas
Some 800 miles southeast of El Paso is the Rio Grande Valley, where rapid growth has overtaken sugar cane and cotton fields, and sleepy hamlets are now thriving cities. More than 1.2 million people live in the two border counties on the U.S. side of this southernmost tip of Texas, and a similar number are directly across the border in Matamoros and Reynosa.
Here, illegal crossers can quickly slip into communities without being forced to trek for days through wide-open spaces.
Part of the solution was the border fence, and 400 landowners - most of them in this part of Texas - had property seized to build it. The fence divided people from swaths of their own land, and also struck many in the region as an offensive gesture toward its Mexican sister cities.
More effective, locals said, has been the influx of Border Patrol agents - 2,546 in the Rio Grande Valley today, almost seven times more than 20 years ago.
Some agents still patrol on horseback. Others are aided by night-vision goggles and unmanned Predator drones watching from 19,000 feet overhead.
Definitions of a secure border vary, but there's agreement that the premise should not stand in the way of immigration reform.