You'd expect to find nuns who have taken solemn vows of chastity, obedience, and poverty to dedicate their lives to praying, singing and praising God.
Sister Brenda, Sister Rose, and Sister Azucena, fulfill all those obligations, but they have another mission, to evangelize Hispanics who've relocated to North Dakota's oil fields.
The professed Daughters of Immaculate Mary of Guadalupe, dressed in traditional habits and gray cardigans, routinely work Williston's Walmart parking lot, greeting customers and handing out flyers welcoming shoppers to join them for Mass.
Sister Brenda Hernandez says the flyers they pass out promote church attendance in both Spanish and English.
"Walmart is a perfect place, because people around Williston come every day for shopping and we can meet them and invite them to come and worship God with us at the Saint Joseph Church Spanish Mass."
These Guadalupanas also make house calls.
Mayra Diez is just one of the many new residents the sisters have befriended. Diez moved to North Dakota from Mabton, Wash.
She is just one of the hundreds of Latino laborers who are now more involved in worship services thanks to the Mexican missionaries.
Diez says she attends the Spanish Mass because of the nuns.
"It's hard to find that connection with the church so having somebody that speaks the same language makes us want to go to church more," Diez said.
Since the sisters began their hand to hand outreach campaign, attendance for the Spanish Mass has almost tripled to nearly 135 people.
Rev. Russell Kovash says a Catholic Extension Society grant covers the cost of the sisters' missionary work and he says the investment is paying off.
"People are drawn to them because they know Jesus. We have a lot of people here who are hungry for God, and the sisters bring God to them."
The three nuns have also connected with children at Saint Joseph's school. They teach religion classes, help prepare students for the sacraments and are popular playmates on the playground.
It's been 15 years since a religious order sent women to work in Williston and Sister Brenda says the reactions they receive reflect that.
"Most of them have never seen nuns like us."
Because of the overwhelming influx of oil workers, these nuns are always on the run, driving to Walmart to had out flyers, making home visits, or going wherever they are called to proclaim the Gospel to migrants.
Sister Brenda says the people they help are very grateful.
"We hear their needs, their hopes, their fears, that is our main purpose."
For the time being, the sisters will continue to evangelize around Williston, but in the future, they plan to take their missionary work on the road in their 1996 Buick, reaching out to Hispanics in the oil producing communities of Stanley, Minot and Dickinson.