Colorado grew on a wave. The wave is gone.

By Shaina Cole | Contributing Writer, Rocky Mountain Voice

Colorado crossed six million people in 2025, according to the U.S. Census Bureau. Headlines called it a milestone. What they didn’t report is how the state got there, and what’s left now that the wave behind the growth has receded.

The Census Bureau’s Vintage 2025 population estimates, released across state, county and municipal data, include a breakdown most coverage did not examine.

The growth wasn’t coming from where it used to

From 2015 through 2019, Census Bureau historical data shows Colorado averaged roughly 50,000 net migrants a year. Most were Americans who had sized up their options and chose this state.

Then it changed.

In 2020, Colorado received a net 239 international migrants. By 2024 that figure was 53,313. At the same time, Americans choosing to come here collapsed to near zero. 

At the same time, Americans choosing to come here collapsed to near zero. From 2021 through 2024, the state averaged 5,700 net domestic arrivals per year — less than one-eighth the pre-surge pace.

The population numbers kept growing. They just weren’t growing because of Americans moving to Colorado anymore.

Colorado net migration by type, 2020–2025. Chart: RMV analysis of U.S. Census Bureau, Vintage 2025 Population Estimates.

The Census Bureau’s numbers for 2021 through 2024 show Colorado gained 137,251 net migrants. But 114,623 of them, or 83.5 percent, arrived from outside the country. 

The domestic migration that had made Colorado a destination for a generation had stalled. The state was still adding people. It just wasn’t attracting Americans the way it used to.

The cliff

In 2025, the international wave collapsed. Net international migration fell from 53,313 to 15,356, a 71 percent drop in a single year.

With it went Colorado’s growth numbers.

The state grew by 76,262 people in 2024. In 2025 it grew by 24,059. That is a 69 percent decline in raw growth in one year, the steepest single-year drop this cycle. Colorado’s own State Demography Office noted the shift in its January press release, writing that net domestic migration was negative in 2025 “for the first time since 2004.”

More Americans left Colorado than arrived. According to the State Demography Office’s January release, the state is still growing only because births outnumber deaths and because a reduced but still positive international migration flow continues. 

Without births outnumbering deaths and continued international migration, Colorado’s migration balance would have been negative.

The State Demography Office named causes in its March county-level summary. “Reasons for the reduced net migration reflect national trends in slower job growth, relative housing affordability, changes in immigration policy, and fewer people moving due to higher interest rates and aging in place.”

Changes in immigration policy. That phrase appears in the state’s own published data summary.

Components of Colorado population change, 2020–2025. Chart: RMV analysis of U.S. Census Bureau, Vintage 2025 Population Estimates.

What Denver’s numbers actually show

Denver’s population swings tell the story at the city level.

In 2024 Denver gained 14,828 residents, its largest single-year increase this cycle, accounting for nearly one in five of all new Coloradans that year. Then in 2025 it lost 978. A swing of 15,806 people in 12 months.

The Census Bureau’s county data shows Denver has been losing domestic residents since 2021 with 25,336 net American departures over five years, negative every single year. International migration, which added 29,702 people over the same period, was the only reason the city didn’t shrink below its 2020 count. Arapahoe County absorbed 31,420 in domestic losses the same way, offset by 34,854 international arrivals that are now arriving at a fraction of prior levels.

Those are not declining places in the traditional sense. They are cities and counties where domestic residents were leaving while international arrivals masked the outflow. When the arrivals slowed, the underlying trend became visible.

Cumulative net migration by type, 2021–2025. Chart: RMV analysis of U.S. Census Bureau, Vintage 2025 Population Estimates.

Where Americans are actually going

The counties growing without the wave are a different picture entirely.

Weld County’s growth story is almost entirely American. Of the 34,226 net migrants it added from 2021 through 2025, 29,361 came from domestic moves — 86 percent. Douglas County is similar: 25,508 of its 30,200 net migrants were Americans choosing to relocate there, not international arrivals. 

Weld County led all Colorado counties in raw population gain from July 2024 to July 2025, adding 7,146 residents according to the State Demography Office’s March release. 

Douglas followed at 6,345, with Adams at 5,411, El Paso at 4,684, and Larimer rounding out the top five at 3,092. Elbert County, southeast of the metro and small enough to get lost in most coverage of Colorado growth, posted the fastest growth rate in the state at 4.1 percent. 

Top county population gains, July 2024–July 2025. Chart: Rocky Mountain Voice analysis of Colorado State Demography Office data, March 2026.

The office’s release also documented a less celebrated trend. Since the 2020 Census, 24 of Colorado’s 64 counties have lost population, with Jefferson, Boulder, and Eagle recording the steepest declines.

The accounting that hid it

Part of what made the population numbers look healthy even as domestic migration cratered is a feature of how the Census Bureau counts people.

When someone moves from another country to the United States, that move counts as international migration. But if that same person later moves from Colorado to another state, the Census Bureau counts it as domestic out-migration. The international arrival and the domestic departure are recorded as two separate events, adding to one column and subtracting from another.

The State Demography Office acknowledged this in its January press release, writing that the large influx of international migrants to Colorado between 2022 and 2025 “has been largely composed of humanitarian migrants, some of whom did not intend Colorado to be their final destination within the United States.” Its March release added “at least some portion of the domestic out-migration is made up of recently arrived international migrants (arriving between 2022 and 2024) who have moved to other states as Colorado was not their intended final destination.”

That mechanism helped lift the 2024 growth numbers and deepen the 2025 decline. At the state level, the State Demography Office says at least some portion of those counted as leaving in 2025 were the same international migrants counted as arriving in prior years.

What’s left

Colorado is still growing. The State Demography Office said in January that the state’s population “continues to grow,” and the Census data shows international migration remains positive, if well below recent peaks.

But the growth story of the last four years was not what it appeared to be. 

The state did not attract 137,251 new arrivals because it became more affordable, because its economy outperformed or because Americans across the country decided Colorado was the place to be. 

It attracted them through a humanitarian migration wave, one the state’s own demographers say was largely composed of people who did not intend Colorado to be their final destination, while the Americans who had been choosing Colorado quietly stopped coming.

The wave is gone. What’s underneath it is a state where more Americans are leaving than arriving, where 24 counties are smaller than they were in 2020 and where some of the cities and counties that built their identity around growth are now confronting a very different reality.