The Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS) is a polygamous sect straddling the Utah and Arizona state lines; the twin towns of Hildale, Utah, and Colorado City, Arizona, are known collectively as Short Creek (pronounced "crick"). The FLDS split off from the mainline Mormon (LDS) church in 1890 after the church denounced the principal of plural marriage. The FLDS believe they are practicing the one true religion as Prophet Joseph Smith intended it to be. Mormons, however, take care to denounce the FLDS "polygs" as having absolutely no relation to their Latter Day Saints.

"It wasn't until I left the FLDS and moved away from the community that I realized I'd been to an unusually high number of funerals growing up in the Creek," says Alyssa Bistline over a crackling phone connection. "Outside, people don't die that often, and usually they're really old."

I'm driving around Short Creek with Alyssa—who is in Boise, Idaho, where she is a college sophomore—piped in through the bluetooth-enabled speakerphone in the rental car I'd picked in Las Vegas the previous night. She is guiding me all around town, following my route, turn by turn, on Google maps. We pass the house she grew up in with her mother, three eldest brothers, and father before he was kicked out of the cult. She directs me to the houses she lived in after that: her stepdad Jim Jessop's home; then the rotten, roach-infested house she and her mother shared with nearly two dozen cousins and friends after being removed from Jim's following the Judgment. I pass the dairy, the zoo, the park, the former birthing clinic, the condemned high school built on a foundation of adobe bricks, and so on. Eventually, I pull up to the corner of Canyon Street and Jessop Avenue , where I find the baby cemetery.

In 2006, Warren Jeffs, then the president and prophet of the FLDS, was arrested and charged with accomplice rape, for just two of the underage marriages he had arranged. In 2011, Jeffs was sentenced to life in prison, plus 20 years. Through his brother Lyle— Bishop of the FLDS and mouthpiece for his imprisoned brother—Jeffs enacted a Judgment wherein FLDS members were asked a series of bizarre personal questions; their answers were judged, and the most righteous were welcomed into the United Order of FLDS elite. Those who did not make it into the UO were separated from their families, placed in patchwork homes of other UO "orphans," and told to repent.

The quick answer for why this polygamous community has buried so many of its children is inbreeding, according to community members. Almost everyone here is some variation of cousin, and, until Warren was locked up and decided to put a hold on all marriages, most men and women were paired together in order to preserve certain esteemed bloodlines. Sisters married the same man in polygamous celestial weddings; brothers from one family married sisters from another (meaning their kids are double cousins). And, because this cult is so tight-knit and averse to strangers, the gene pool is rather limited.

There are baby graves year that date back as earlier as the 1950s, potentially even earlier: many are unmarked. The last infant grave marked in this cemetery is dated 2010; Warren issued an edict from prison banning sex in 2011, so few infants have been born since then (the few babies born each year are the product of institutionalized rape by cult-appointed seed bearers ). There are also graves lacking any dates whatsoever. Some read simply, "Baby Keate," or "Baby Bateman," or "Baby Cooke," with holes where numeric date tiles might otherwise be placed.

The lot is unmarked and unremarkable. There is no sign. A scrappy white wooden fence runs the length of it along Canyon Street. It is bordered to the north by a well-maintained lot where there sits a stately red brick home with UEP (United Effort Plan, the church trust which is now controlled by the state of Utah in the aftermath of Jeffs' conviction) spelled out in white brick on its south-facing side. At the lot's northwest corner, a metal gate—the kind you might find on a cattle ranch—hangs open on its hinge. The baby cemetery is a mess of overgrown weeds and dry, cracked dirt, home to hundreds of infant and toddler-size graves, not all of them marked. Many of the souls interred here lived not longer than a day, some just two days, two weeks, or two years. Some feature more expensive-looking gravestones, and include, beyond names and dates, terms of endearment such as: "Sweet baby girl," "Our son," and "Heaven's very special child." Still more, rather cryptically, feature child-size palm and footprints.

And then there are the more livable genetic conditions. The most common birth defects for children born of close cousins, anywhere, are: harelip, cleft palate, clubfoot, and certain forms of heart valve conditions. These conditions are disproportionately common, relative to the size of the general population, in Short Creek. According to many of the individuals interviewed for this story, these children are seen as special angels sent from God to the FLDS community. They're given the utmost attention and care because the FLDS faithful believe everything in this life is a test before entering the celestial kingdom, and caring well for all of Heavenly Father's children is part of that test.

Fumarase deficiency, however sensationalized, is not the only genetic disorder found here. One man, who asks to remain nameless to protect his and his family's privacy, describes a lifetime of round-the-clock care and too-frequent hospital visits for his five sons. His eldest died six years ago at 10 years old, he says, and another died in infancy, leaving behind two remaining brothers from a set of spontaneous identical triplets. Those two—and a fifth boy—also suffer from the condition that all of this family's sons were born with: x-linked hydrocephalus . A rare neurological disorder characterized by water on the brain, muscular stiffness, adducted thumbs and aphasia, x-linked hydrocephalus is expressed only in men and carried by women. "You have to either accept" the responsibility of caring for so many children with major healthcare needs "or let it destroy you," says this man, whose wife recently suffered a stroke. The knowledge that one's children are likely to be born with conditions like this one does not prevent FLDS couples from becoming pregnant; instead, they see it as a responsibility and blessing to have many children.

The FLDS started out as a few fringe families in the late 1890s; as more seeking to follow the principal of plural marriage moved to the polygamous towns in the early-to-mid 20th century, the gene pool grew, but by the 90s, under the stricter control of prophet Rulon Jeffs (Warren's father), they were tightening up and selectively marrying and breeding in a sort of misfired eugenics experiment that ultimately yielded its own genetic disorder: fumarase deficiency (FD), otherwise known as Polygamist Down's . Fumarase deficiency (FD) is an autosomal metabolic recessive disorder, meaning it is necessary for an individual with the condition to receive the mutant allele from both parents. Those affected by the genetic disorder suffer grand mal seizures and often have facial feature deformities and severe mental retardation, with IQs as low as 25. A simple urine test will reveal whether there is an excess of fumaric acid in the urine, if the other, more external symptoms aren't obvious enough. Until the 1990s, there were only 13 known cases of FD in the world. But by 2006, Dr. Theodore Tarby, of Arizona, had discovered at least 20 more children living with the condition in Short Creek, all within just blocks of each other.

Dawna Black Bistline (Alyssa Bistline's father's brother's wife) has seen firsthand how the children of cousins suffer. Two of her sisters married their first cousins—men with whom they share the same grandfather; the sons of their father's second wife, who is their mother's full sister. One of her brothers married a woman whose grandmother is a sister to their father. "My father and her grandmother were full brother and sister," she explains, recognizing the bloom of confusion on my face. "And she's not the only one; three of her sisters married three of my brothers. And another one of her sisters married one of my half-brothers, but we have the same blood and genetics because our moms are full sisters." Dawna's husband is a brother to her older sister's husband, "but they're only half brothers, so him and I aren't blood-related at all, because he was from the youngest mother, which had no relation to us other than marriage, and then my sister was married to the older brother and his mom and my grandmother were full sisters."

"How do you keep track of that?" I wonder aloud.

"Well, needless to say, we had a lot of, uh.... Well, my sister had a little baby with a cleft lip; it was her first child and it had a cleft lip and cleft palate, because they were both Jessops, and Jessops are carriers of that gene. She also had a child with a clubfoot, and I think probably half of her children had respiratory problems when they were babies, because they were so related."

There are times when it has gotten kind of gross, like when they marry an uncle to a niece.

Dawna's younger sister has a little boy with two clubfeet. That sister, too, dealt with a lot of respiratory problems with her kids, "because of the relation," Dawna explains. "It's not really talked about; I don't think [people here] even research to see how related they are" before getting married or pregnant, she adds.