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 give pause.

Now, 20 years after that onslaught, crossing would mean scaling two fences (one topped with coiled razor wire), 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.”