The sheriff’s department in the Ajo district of Pima County operates as a kind of self-sufficient outpost of the county sheriff’s department in Tucson, some 140 miles east. Most shifts are covered by four staff members — two deputies, a corrections officer for the 21-bed jail and a 911 dispatcher — who are responsible for a brutal 3,000-square-mile stretch of terrain between the Arizona-Mexico border and Phoenix, 110 miles to the northeast.

The Pima County Sheriff’s Department collaborates with federal agencies like the Border Patrol, Customs and Border Protection, and the Fish and Wildlife Service. The alliance of agencies is called the Border Anti-Narcotics Network. The network made 440 drug seizures in the first quarter, netting 18,000 pounds of marijuana, according to Lieutenant Clements. That’s 2,500 pounds more than the first quarter of last year.

Lieutenant Clements attributed that to “increased technology and more officers in the field.” Still, he said, there is no way to know how many illegal drug shipments are making their way northward, undetected.

What does a law enforcement officer have to do to end up in a place like this? Some deputies out of the police academy, eager to make their mark and ascend department ranks, agree to serve three years in Ajo. Most leave after their required stint expires.

Back in Tucson, a deputy who chose to put in his time at the desert outpost joked that he did so without realizing what he had signed up for. “Nobody told me I wasn’t supposed to check the box,” said the deputy, Jesus Bañuelos, who served three years in Ajo before becoming a spokesman for the sheriff’s department.