These are among the findings from statistics The Salt Lake Tribune obtained through a public-records request.
Utah's predominant faith, The Church of Jesus Christ of Latter-day Saints, provides county-level membership numbers to state government for demographic purposes. The Tribune compared these figures with census estimates to come up with a percentage of the population that is Mormon.
In 22 of the state's 29 counties, that percentage rose last year. The biggest driver appears to be the reduction in people moving to the state since the economic collapse in late 2007 and early 2008, according to demographer Pam Perlich at the University of Utah.
Before that, The Tribune had tracked a long, slow descent in the percentage of Utahns on Mormon membership rolls.
Since 2009, that trend has reversed, and the LDS percentage has been inching up. In 2005, more than 36,000 people moved into Utah, according to statistics compiled by Perlich. That influx dropped to below 5,000 a year this decade.
The state's population has increased far more than that, driven by Utah's highest-in-the-nation birthrate. In 2013, Utah added 46,000 people, according to the Census Bureau 78 percent of them came from Utahns having children.
"A lot of that internal growth is going to be traditional Utah populations," said Perlich, noting that the fastest-growing cities dot northern Utah County and southern Salt Lake County, which she described as "Mormon enclaves."
She also noted that demographers increasingly have seen people self-segregate, and she hypothesizes that the growth in Utah and southern Salt Lake counties is partly based on Mormons moving there from other parts of the state.
The two counties, the state's most populous, have far different Mormon populations.
Utah County, home to LDS Church-owned Brigham Young University, is one of just three counties with a Mormon rate that tops 80 percent, and it has become increasingly LDS in recent years.
In 2013, the Salt Lake City-based faith reported adding 12,815 members in Utah County. That number is startling, given that the Census Bureau estimated the county's overall population rose only 11,300 that year. Utah County is 82.26 percent Mormon.
For years, Salt Lake County had seen its LDS percentage decline. It appeared to be on track to become Utah's fifth county with a minority Mormon population when its LDS percentage dipped to 51.32 percent in 2012. But it bucked the trend in 2013 and saw its percentage rise to 51.41 as the LDS Church recorded an increase of 9,061 members.
South Jordan Mayor David Alvord was surprised by the numbers, having assumed Salt Lake County would continue to become more religiously diverse. But he's not disappointed.
Alvord, a Mormon and mayor of the county's fastest-growing city, said he hopes to see that LDS percentage climb.
"As a devout member, I would hope that trend would continue," he said. "I think the church is a good influence on communities."
He said his city has no way to track how many new residents are Mormon, but he notes that the city's two LDS temples (Jordan River and Oquirrh Mountain) have drawn Mormons to the area, either from Utah or from nearby states. Alvord said the bishop of his LDS ward is a recent California transplant. In fact, South Jordan is the only city in the world with two Mormon temples within its boundaries.
Provo, the Utah County seat, will become the second such city when the Provo City Center Temple (in a restored historic Provo Tabernacle) opens downtown, joining the 1970s-era Provo Utah Temple in the foothills northeast of BYU.
Eight of the state's 17 operating or announced Mormon temples are in Salt Lake and Utah counties.
The four Utah counties where less than half of the population is Mormon are Carbon (47.05 percent), San Juan (39.70 percent), Summit (30.37 percent) and Grand (27.25 percent). The two counties with the highest LDS percentages are Morgan (86.88 percent) and Rich (85.10 percent).
The LDS Church reports the number of people on its membership rolls, which includes some people who do not go to church and no longer consider themselves Mormons.
email@example.com Twitter: @mattcanham