One county in Utah was a surprising powerhouse for growth during the past decade, adding more people than any other — and in some unexpected ways.

It wasn’t Salt Lake County, which had been the epicenter of Utah’s growth since it was settled by pioneers.

Instead, Utah County became the growth champion of the 2010s, according to estimates released Monday by the University of Utah’s Kem C. Gardner Policy Institute, which handles state-generated population estimates.

“Salt Lake County obviously still has a lot of jobs and a lot of people. But Utah County is really starting to take over that growth,” said Emily Harris, a demographer at the institute.

From 2010 to 2019, Utah County’s population ballooned by 26.1% — adding 134,845 people, equivalent to the size of West Valley City, the state’s second largest city.

Meanwhile, Salt Lake County added 123,305 people in the decade — 11,540 fewer than its neighbor to the south — up by 12%.

(Christopher Cherrington | The Salt Lake Tribune)
(Christopher Cherrington | The Salt Lake Tribune)

Utah County has long been known for high fertility rates and many babies. But for the first time, Harris notes, more of its growth in the past year came from immigration than births, 50.1% to 49.9%.

“To me, that’s just a really strong signal of Utah County’s trajectory” continuing as a magnet for people to move there, she said, attracted by more affordable housing and high-tech jobs such as at Silicon Slopes.

Pam Perlich, senior demographer at the institute, said that trend is likely to continue — as fertility rates in the county (and statewide) fall and deaths rise as the population ages, and outsiders flock to Utah County’s growing jobs and cheaper housing.

Perlich said few people would have predicted such change in Utah County 20 years ago or even 10 years ago.

She said that before Geneva Steel closed in 2001, Utah County “used to be basically farming, Geneva Steel and BYU.” When Geneva Steel shut down, “you actually saw an outmigration. ... It was a lot of open spaces and a lot of beautiful agricultural land.”

As the Wasatch Front’s economy heated up after the recession, that beautiful agricultural land ended up attracting Silicon Slopes and other industries, and affordable housing. The quickest growing areas on the Wasatch Front became northern Utah County and southern Salt Lake County.

“I don’t think people could have anticipated just how quickly the Silicon Slopes phenomenon would have emerged and just how quickly land-use policies changed,” Perlich said. “I mean, we’ve got actual multifamily dwelling units in little cities across Utah County, including places you wouldn’t think of like Spanish Fork.”

(Chris Detrick | Tribune file photo) Construction on new buildings in Vineyard City on May 23, 2017. Vineyard has been the nation's fastest growing city in recent years, helping Utah County to grow faster than Salt Lake County this decade.

She foresees that growth continuing there — and that it may change Utah County dramatically.

“It will become more multicultural, multilingual and and multiethnic — just more cosmopolitan and diverse,” Perlich said. “Salt Lake County will still likely lead in that regard, but Utah County will become more like Salt Lake County — one big urban area.”

Perlich said projections indicate that by 2065, the Wasatch Front will grow into one large metro area akin to present-day Seattle (which has 3.7 million people) — with the bulk of the population in Salt Lake and Utah counties.

Will Utah County ever pass Salt Lake County in overall population?

“It depends on so many things,” Perlich said, but it might be possible depending on decisions about such things as mass transit, zoning and how the new inland port in Salt Lake County affects growth and jobs there.

Perlich said unseating Salt Lake County would be difficult because “the employment centers are so dominantly in Salt Lake County. It's still the economic heart of the state.”

Other estimates in the new data show that growth in Utah may be moderating but is still large.

Last year, Utah added 53,596 people, up 1.7%.

“Growth kind of peaked in 2017. Now it has kind of stabilized around 1.7% for the last two years,” Harris said. “That probably has to do with the kind of growing pains that Utah has been experiencing associated with that growth, such as [the lack of] affordable housing.”

During the decade, Utah expanded by 456,377 people, up 16.5%

By percentage rate, a few counties that ring the Wasatch Front actually grew faster than Utah and Salt Lake counties during the decade.

Wasatch County grew by 30.7%; Morgan by 28.7%; Tooele by 21.8%; and Juab by 21.6%.

Southwest Utah also saw some large growth by percentage, including 30.7% in Washington and 21.6% in Iron. Harris notes that the St. George area is not just attracting the retirees for which it is famous, but is luring all age groups among new immigrants.

Washington County also led all counties for its growth rate in 2019: 5.56%, as it added 9,508 people.