To the police and residents, the violence shows how a modern-day gold rush is transforming the rolling plains and farm towns where people once fretted about a population drain. Today, four-story chain hotels are rising, and small apartments rent for $2,000 a month. Two-lane roads are jammed with tractor-trailers. Fast-food restaurants offer $300 signing bonuses for new employees, and jobs as gas station attendants can pay $50,000 a year. Workers flush with cash are snapping up A.T.V.s, and hotel menus offer crab and artichoke dip and bacon-wrapped dates.

Amid all of that new money, reports of assault and theft have doubled or even tripled, and the police say they are rushing from call to call, grappling with everything from bar brawls and shoplifting to kidnappings and attempted murders. Traffic stops for drunken or reckless driving have skyrocketed; local jails are spilling over with drug suspects.

Last year, a study by officials in Montana and North Dakota found that crime had risen by 32 percent since 2005 in communities at the center of the boom. In Watford City, N.D., where mile-long chains of tractor-trailers stack up at the town’s main traffic light, arrests increased 565 percent during that time. In Roosevelt County in Montana, arrests were up 855 percent, and the sheriff, Freedom Crawford, said his jail was so full that he was ticketing and releasing offenders for minor crimes like disorderly conduct.

“I don’t have nowhere to put them,” Sheriff Crawford said.

Officials say that most of the new arrivals are hard workers who are simply looking for better lives, and that much of the increase in crime has resulted from population growth: Waves of new residents inevitably mean more traffic crashes and calls to 911.

Police and sheriff’s departments are responding by hiring more officers, in part with new tax revenue but often not fast enough to keep pace with their booming populations. In Dickinson, for example, the population has surged to an estimated 25,000 from 16,000 in 2000, with new hotels, condominiums and extended-stay inns being built every week. The city’s police department has 38 officers, but Sergeant Klauzer said it would need to add 12 more to keep up with the growth. Each detective’s caseload has doubled.