The Bakken reserve is named for North Dakota farmer Henry Bakken who owned land where the first well was drilled and pumps an estimated 1.01 million barrels of oil per day, having reached its billionth barrel in August, according to a U.S Chamber of Commerce report. The reserve itself is estimated to contain more oil than all of Saudi Arabia and is likely to produce crude at its current rate for 30 more years.

All that light, sweet crude has business booming in Williston, but there are negatives as well as positives to this economic gusher. Western Cooperative still makes agricultural loans, but the market hasn't grown since oil royalties became the new cash crop for many local landowners.

That's only one of many challenges facing area residents and the credit union, Stillwell said.

“I have been in credit unions since 1986 and I have to say that the past five years have been the most difficult in terms of finding ways to meet the challenges,” she acknowledged.

Some of those challenges are typical to any fast-growth environment, while others are unique to Western Cooperative and its members.

Foremost among those challenges has been the rapid-fire growth sparked by the oil field, first discovered in 1951 but only recently tapped in a significant way. In the past five years, Williston's population of about 12,000 has tripled to somewhere north of the mid-30s, Stillwell said. The rapid growth has put a strain on area infrastructure and housing.

“Someone did a national study and found that the most expensive place to live in the U.S. was Williston, N.D,” Stillwell said. “Yet, we still have a volunteer fire department.”

The demand for housing is so great that a three-bedroom apartment, if there are any available, rents for $3,000-plus per month, according to local home statistics. That may be fine for oil company workers that make a minimum of $90,000 per year without a high school diploma. But when it comes to service workers, including employees at Western Cooperative, the cost of living has often outpaced income levels.

The local McDonald's made national headlines in 2013 for paying its starting workers $17 per hour in an attempt to keep them from running off to work in the oil fields. Stillwell said the credit union, which has eight branches in six area communities, pays in the same range for the same reason.

“Cost of labor is a big issue and we struggle finding front-line employees,” Stillwell said. “The state's unemployment rate is 2.8%, but our county has had less than 1% unemployment for several years. It's very difficult to find employees when you're competing with high-wage jobs.”

The influx of new residents has proved less of an economic boon than a burden for many in the community, Stillwell noticed. In addition to driving real estate prices up, many workers live in “man camps,” which are dormitory structures near the drilling fields, and have no permanent local address. This disqualifies them from joining the credit union, according to Stillwell.

Read more: Big oil paychecks inflate cost-of-living …

Big oil paychecks may mean there is lots of money floating around, but the effect on Western Cooperative's loan demand, while steady, has been mixed, Stillwell said.

“We have a huge demand for real estate loans, but the price of homes is quite high,” “CFPB requirements have made the cost of compliance and the time it takes to close a real estate loan so much longer than it was before.”

The credit union also is limited by the lack of lending staff required to handle loan demand.

“That's the challenge of doing business in a really busy place,” Stillwell said.

Consumer loans are hard to attract because members have the ability to pay cash even for larger purchases, Stillwell said. Even the credit union's agricultural loan portfolio, which once grew at 5% to 10% per year, has stagnated, Stillwell said. Western Cooperative has approximately $55 million in ag loans, $20 million in real estate loans and around $18 million in commercial loans, she pointed out.

Many of the landowners are making substantial sums in oil royalties for wells drilled on their land and have either minimized their farming efforts or are covering costs for which they previously would have taken out loans.

The loss of that loan growth is further complicated by deposit challenges each time a landowner comes in to deposit a royalty check, some of which range between $3 million and $5 million, according to some oil production industry estimates.

“We've had to tell many of them that we can't accept the full amount and that they should consult a financial planner,” Stillwell said. “Sometimes, they don't understand and say, 'But this is my credit union and I've always come here.'”

Controlling growth has been a struggle over the past five years, according to Stillwell. At times, the credit union has grown between 25% and 30% at over a short period of time, and Stillwell has had to put the brakes on growth more than once.

The difficulty with making consumer loans has left Western Cooperative with $160 million of its $345 million asset level in various safe investments, according to Stillwell. The $185 million in total loans has led to a loan-to-share ratio of 50%, much lower than the 80% to 90% Stillwell would prefer. Still, the credit union's 9.5% equity ratio is strong.

“NCUA understands because they're seeing the same thing throughout the state,” Stillwell said. “But they aren't looking at the fact that half of our assets are not at risk. They're sitting in a fairly liquid investments or cash accounts, and our CAMEL rating is good,” but would not disclose it due to NCUA restrictions.

Despite the challenges posed by the oil boom, there are also some slivers of success, Stillwell said, not the least of which is income and opportunities for the next generation of workers. While some young people struggle elsewhere to find well-paying jobs, those who live in Williston may have their future all sewn up.

“There's a lot of opportunity for the 25-to-40 year olds,” Stillwell said. “They're already finding themselves in management jobs they otherwise wouldn't have gotten at that age just because the demand is so great.”

North Dakota's oil industry will continue booming for years to come, she predicted. Even if prices go down and active drilling ceases, there will still be good jobs in oil production demanding both trained and untrained workers.

Meanwhile, Western Cooperative has learned to prosper and safely grow in the midst of Williston's boomtown mentality.

“We've never seen something like this before and to me, it's all a little bit of a work in progress to me,” Stillwell said. “We had to start making adjustments and going day by day. Now we're back to controlling the level of our growth and gaining stability in the work force.”

Then, of course, there's all the money. For a time, it was rumored that General Motors sold more Chevy Corvettes in Williston, N.D., than anywhere else in the world. That was news even to Stillwell.

“I don't know about that, but it sounds like something that could very well be true,” she said.