NACO, Ariz. — John Ladd has two old pickups he uses to bang around his ranch, which rambles for 10 miles beside the Mexico line. One’s a red Chevy that not long ago carried the body of yet another border crosser who had died on his property. The other is a blue Dodge with better shocks, and that’s what he is driving now, along an unpaved road in an unincorporated place called Naco.

To his immediate right, cattle roam the mesquite and grass of his family’s 16,000-acre ranch. To his left, a mix-and-match set of interlocking fences slices into the distance, this one 12 feet high, this one 18 feet high, this one a metal mesh, this one a vertical grille, section after section after section.

Mr. Ladd, 61, looks and acts the way a rancher is expected to, with brush mustache, hard squint and matter-of-fact affect, all kept tight under a sweat-stained cowboy hat. Bouncing westward, he points to spots where fencing had been peeled in the past like an upturned can of Spam. In the last four years, he says, more than 50 vehicles have rumbled through fence cuts and across his property.