“I was sleeping, and I heard a very big bang and then shouting,” she recalled. “Someone was yelling through a bullhorn, although I couldn’t hear what they were saying. There was a helicopter overhead, and out the window I could see red lights flashing and a lot of people with guns.”

They were agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives, Immigration and Customs Enforcement and the Drug Enforcement Administration. They led away in handcuffs Columbus’s mayor, police chief, village trustee and numerous others accused of smuggling guns, ammunition and body armor across the border to Mexican outlaws.

Columbus, with 1,800 residents, sits just across the border from Las Palomas, a Mexican town about 75 miles west of El Paso. Many families have relatives on both sides of the line. Hundreds of children cross every morning from Las Palomas to attend school in Columbus. But drug violence has strained the relationship. Columbus residents recount how the mayor of Las Palomas was killed some years back and how a popular dentist was taken away, never to be seen again. Although such violence has not spread to Columbus, residents say, the influence of the drug trafficking groups in Las Palomas has definitely reached north.

“We don’t like to say much because we don’t want to lose our lives,” said Mr. Dean, the historian.

The arrests and the guilty pleas that some of the defendants have entered, though, speak volumes.