Throughout American history, religious groups have walled themselves off from the rhythms and mores of society. St. Marys isn’t nearly as cut off from modern life as, say, the Amish communities that still abjure all modern technology, be it tractor or cellphone. Residents watch prestige television on Hulu and catch Sunday-afternoon football games; moms drive to Topeka to shop at Sam’s Club. Yet hints of the town’s utopian project are everywhere. On a recent afternoon, I visited the general store, where polite teens played bluegrass music beside rows of dried goods. Women in long, modest skirts loaded vans that had enough seats to accommodate eight or nine kids—unlike most American Catholics, SSPX members abide by the Vatican’s prohibition on birth control. At housewarming parties and potluck dinners, children huddle around pianos for sing-alongs.

In their four decades in St. Marys, the followers of SSPX have more than doubled the town’s size. Even with six Masses on Sundays, parishioners fill the Society’s chapel to capacity; overflow services are held in the gym of the Society’s academy, which inhabits an imposing campus built by the Jesuit missionaries who called St. Marys home in the 19th century. The school is constantly running out of classroom space. The parish rector, Father Patrick Rutledge, has to scramble each summer to accommodate rising enrollment. Real estate sells at price points closer to those of Kansas’s big cities than of its other small towns.

Newcomers are attracted by the opportunity to live beside like-minded neighbors. But many are pushed here as much as they are pulled. When they lived in other places, many SSPX families felt isolated by their faith, keenly aware that their theological convictions were out of step with America’s evolving cultural sensibilities and what they perceive as the growing liberalism of the Catholic Church, especially on issues such as gay marriage and abortion. They were wary of being labeled bigots by co-workers and even friends. They worried that their children would be exposed to sin: A friend’s parents might let their kids watch violent television shows; teens might encounter pornography on a classmate’s phone. “We can’t keep things out that we’d like to keep out completely,” Rutledge told me. But the environment in St. Marys is “as conducive as possible for children to save their souls.”