That domination - at least in terms of raw numbers - appears to be nearing its end.
Within the next three years, the Mormon share of Utah's population is expected to hit its lowest level since The Church of Jesus Christ of Latter-day Saints started keeping membership numbers. And if current trends continue, LDS residents no longer will constitute a majority by 2030.
These projections are based on normally secret membership counts the LDS Church voluntarily hands over to Utah's Office of Planning and Budget, under what it assumed was a binding confidentiality agreement. The state planning office uses the county-by-county numbers to help estimate future population growth.
Through a public records request, The Salt Lake Tribune obtained the data from 1989 to 2004. State employees believe the LDS Church has provided the records since at least the 1960s but could retrieve only the numbers for 15 years and found no such confidentiality agreement.
Still, these 15 years are enough to identify a historic transformation in the makeup of Utah's ever-growing population.
Stated simply: "Utah is essentially becoming more like the nation," said Robert Spendlove, the planning office's lead demographer.
Slow shift: The religious shift is likely to alter the civic discourse, but that doesn't mean Utah's LDS-dominated culture or conservative politics will dramatically change anytime soon. Rather, academics say, it will morph over time as non-Mormon births and move-ins continue to whittle away at the percentage of Utahns who are LDS.
As University of Utah sociologist Theresa Martinez said: "The core LDS population will always be a force here. In your lifetime, I am sure it is not going to change that much. It will probably be more diverse but the power structures will probably remain the same."
The often cited claim that Utah is 70 percent Mormon is not true - and hasn't been true for more than a decade, according to the church numbers. While continuing to grow in actual members, the LDS share of the state population showed a slow but constant decline every year from 1989 to 2004.
According to the 2004 count, Utah is now 62.4 percent LDS with every county showing a decrease.
LDS Church officials declined interviews. But they issued a statement in response to questions submitted by The Tribune: "The church has always extended a hand of friendship and fellowship to those of other faiths, and will continue to do so."
The LDS Church said its count comprises "all members" - including children in LDS families under age 8, when most Mormons are baptized, and nonpracticing members.
Professor Tim Heaton, who studies LDS demographics for church-owned Brigham Young University, says the county numbers probably come from church membership rolls, and that between half and one-third of those people are not active in the faith. If that's true, then, at most, 41.6 percent of Utahns are church-going Mormons.
Broken down, the numbers spotlight trends The Tribune will explore in articles today, Monday and Tuesday:
l On the county level, the LDS Church has consolidated congregations in some affluent Salt Lake County neighborhoods after young families relocated to the big, and more affordable, homes in northern Utah County.
l Washington County is growing at the state's most rapid pace and the LDS Church can't keep up with the need for new meeting places. Still, the percent of residents who are Mormon has fallen below that of the state.
l Even in the least LDS county, it is easier for Mormons to find a sense of community than it is for non-Mormons in the most LDS county.
l Statistics from other sources show the LDS growth worldwide has cooled. Official church membership numbers in some key countries are much higher than the LDS population identified by census counts.
Utah's ongoing religious diversification has little to do with the LDS Church or its teachings, but rather is a reflection of the economy, according to Pam Perlich of the University of Utah's Bureau of Economic and Business Research. Perlich sits on the committee that projects state population growth, in part with the help of these LDS numbers. She also reviewed The Tribune's analysis for accuracy.
"When economic growth goes up, minority population goes up, and this is kind of a code word for non-Mormons," she said.
Utah saw a similar trend in the early 1900s with the mining boom, but once the mines became unprofitable, workers left and the LDS percentage rose again. Steady economic growth through the 1990s, with a slight hiccup a few years ago, has shifted the main reason people move to Utah from religion to jobs.
Immigrants from Mexico, who are not generally LDS and tend to have large families, have greatly influenced this ongoing shift, Perlich said. Still, she expects the LDS share to rise again if Utah's economy tanks, because people who have tenuous ties to the Beehive State will most likely flee for better job markets, Perlich said.
Gov. Jon Huntsman Jr. calls the drop in LDS share "a trend that was largely predictable." He expects it to have political ramifications, since most Mormons tend to vote Republican.
"We will become more balanced between Republicans and Democrats eventually," said the GOP governor who has no problem with Democrats gaining more power in one of the nation's most conservative states. "I have always stood for balance in all things."
While the voting bloc remains just as Republican as it has been since the early 1980s, BYU political scientist Kelly Patterson has observed "a small decline" in the percentage of voters who are LDS, according to exit-polling data after elections. He has found that conservative voters always have comprised 55 percent to 60 percent of the electorate, while the LDS voters declined from 72 percent in the 1984 presidential election to 67 percent in 2004.
Lifestyles and morals: Utah's unchanged GOP bent - along with other ongoing trends attributed to the large LDS population - suggests that many new non-Mormons fit in with the state's lifestyle. Utahns continue to be less likely than the average American to smoke, abuse drugs, die of cancer or give birth as a teenager.
Perlich isn't surprised, saying a non-Mormon is only a person whose religious beliefs differ from that of the LDS Church and that includes people with morals similar to the average Mormon.
"The non-Mormon population is not monolithic," she said. "It has a great diversity within itself."
Huntsman says the decline in Utah's homogeneous population is an outgrowth of the LDS Church's success in attracting converts in other countries.
"The LDS Church becomes more internationalized, the state of Utah becomes more internationalized," Huntsman said. "We become more attractive to all people, not just people from one particular religion, and I think that will continue to be the trend going forward."
Demographers for the state, University of Utah and BYU agree that at least one statistic helps explain the decline in Mormon percentage: the fertility rate.
In the 1960s, Utah women of childbearing age averaged 4.3 children, far surpassing the national average. That number is down to 2.6 children per woman - only a half-percent above the norm.
Growing subcultures: Deciphering how Utah's shifting demographics will change neighborhoods is hard to quantify, BYU's Heaton said. The new religious diversity may spur recharged debates in public schools over long-standing issues such as sex education and the performance of religious songs and prayer at graduation. He also believes the rate of new LDS baptisms will slow.
"As the subcultures of Utah gain strength in numbers, newcomers don't have to turn to the LDS Church to find a sense of community," he said.
But the average Utah Mormon will experience this religious transformation in a more fundamental way, said Heaton, who believes he already has felt it in his booming Springville community.
"When I moved in, I knew everybody in the neighborhood and to some degree their attachment to Mormonism," Heaton said. "But now it is harder to get a sense of your neighborhood."
While Utah's religious diversification is significant, it should not be overstated, Perlich said.
Mormons still make up a "commanding majority in many parts of the state" and will for decades, she said. Even after dropping below the 50 percent mark around 2030, the LDS Church will remain a dominant presence and will define Utah's reputation throughout the world.
"For as long as that church is vibrant," she said, "Utah culture will always be tied to it."