WILLISTON, N.D. — Christina Knapp and a friend were drinking shots at a bar in a nearby town several weeks ago when a table of about five men called them over and made an offer.

They would pay the women $3,000 to strip naked and serve them beer at their house while they watched mixed-martial arts fights on television. Knapp, 22, declined, but the men kept raising the offer, reaching $7,000.

“I said I make more money doing my job than degrading myself to do that,” said Knapp, a tattoo artist with dark streaks in her light brown hair, a bird tattoo on her chest and piercings above her lip and left cheekbone.

The rich shale-oil formation deep below the rolling pastures here has attracted droves of young men to work the labor-intensive jobs that get the wells flowing and often generate six-figure salaries. What the oil boom has not brought, however, are enough single women to provide balance.

At work, at housing camps and in bars and restaurants, men have been left to mingle with their own. High heels and skirts are as rare around here as veggie burgers. Some men liken the environment to the military or prison.

“It’s bad, dude,” said Jon Kenworthy, 22, who moved to Williston from Indiana early last month. “I was talking to my buddy here. I told him I was going to import from Indiana because there’s nothing here.”

This has complicated life for women in the region as well.

Many said they felt unsafe. Several said they could not even shop at the local Wal-Mart without men following them through the store. Girls-night-out usually becomes an exercise in fending off obnoxious, overzealous suitors who often flaunt their newfound wealth.

“So many people look at you like you’re a piece of meat,” said Megan Dye, 28, a nearly lifelong Williston resident. “It’s disgusting. It’s gross.”

Prosecutors and the police note an increase in crimes against women, including domestic and sexual assaults.

“There are people arriving in North Dakota every day from other places around the country who do not respect the people or laws of North Dakota,” said Ariston Johnson, the deputy state’s attorney in neighboring McKenzie County, in an email.

Over the past six years, North Dakota has shot from the middle of the pack to become the state with the third-highest ratio of single young men to single young women in the country. In 2011, nearly 58 percent of North Dakota’s unmarried 18-to-34-year-olds were men, according to census data. That disparity was even starker in the three counties where the oil boom is heaviest — there were more than 1.6 young single men for every young single woman.

And most people around here say the gap is considerably larger. Census data mostly capture permanent residents. Most of the men who come here to work maintain their primary residences elsewhere and split time between the oil fields and their homes. And women note that many of the men who approached them are married.

Some women have banked on the female shortage. Williston’s two strip clubs attract dancers from around the country. Prostitutes from out of state troll the bars.

Natasha, 31, an escort and stripper from Las Vegas, is currently on her second stint here after hearing how much money strippers made in Williston on a CNN report last year. Business in her industry is much better here than in the rest of the country, she said. She makes at least $500 a night, but more often she exceeds $1,000.

“We make a lot of money because there’s a lot of lonely guys,” she said.

On a recent night at City Bar in nearby Watford City, the only women in the long, wood-paneled room were two bartenders and the woman running the karaoke. Under flashing lights, some of the male patrons huddled at the bar, while others played games like simulated buck shooting and darts.

Zach Mannon, 23, who has been working in the oil patch for three years, said he once bumped accidentally into a woman in a bar packed with men. He excused himself, he said, but then her boyfriend came over and accused him of grabbing her buttocks. He denied it. The man insisted they step outside, so they did, but 14 of Mannon’s co-workers from his rig came along. The man backed down, and no punches were thrown.

For Mannon, having women around was more about finding sanity than a soul mate.

“Out here, you can’t tell a guy, like, ‘I had a rough day,’ ” Mannon said. “They’re going to go, ‘Everyone has a rough day. Get over it you sissy.’