In 2025, Colorado hit a new high: 6 million people.
The state had been very close to that mark for years. After adding about 24,000 more residents in the prior 12 months, the population finally pushed past 6 million on July 1. More precisely, it landed at 6,012,561, according to the U.S. Census Bureau.
But 24,000 is such a tiny number compared to 6 million. The annual growth rate was 0.4%, the lowest in decades. It was even lower than the U.S. growth rate of 0.5%.
Last decade, Colorado’s population growth was nearly twice the rate of the rest of the U.S., with the state growing nearly 15% between 2010 and 2020, compared to the nation’s 7.4%.
Growth had been slowing in Colorado for the past decade largely due to shrinking birthrates and more deaths as the population grew older. But in the past four years, the state’s most reliable source of new residents — net migration — took off. And then last year, it went back down.
“More outs than ins,” the state demographer’s office summed up in a statement.
Those leaving were largely “domestic,” or residents who moved to another state. The net loss was 12,100 people. The state did gain 15,356 net new international residents, but that number was down 70% from the prior year’s 58,308 new arrivals from other countries.
Federal policies in recent years contributed to the surge and decline of migration to the U.S. and Colorado over the last years.
In 2023 and 2024, Denver became a bus drop-off location for many Venezuelan migrants claiming asylum after crossing the U.S.-Mexico border in Texas. Last year, Denver Mayor Mike Johnston was grilled by a congressional committee over the city’s efforts to feed and house tens of thousands of South American migrants. Ongoing arrests by Immigration and Customs Enforcement in Colorado have quadrupled during the Trump administration.
The State Demography Office didn’t respond to questions about the changes by deadline but in a news release said the change in migration was “largely composed of humanitarian migrants, some of whom did not intend Colorado to be their final destination within the United States. At least some portion of the domestic out-migration from Colorado is made up of recently arrived international migrants.”
But without the reliable increase in net migration, Colorado increased naturally. Births outnumbered deaths. About 64,380 babies were born in 2025, up 4.6% from the prior year. That was the primary reason for Colorado’s population growth, according to the demographer’s office.
On Tuesday, the U.S. Census Bureau released the latest population numbers for the nation, which also showed a “historic decline” in net international migration. The numbers were cut in half falling to about 1.3 million people from other countries. Growth slowed overall to 0.5% nationwide, an increase of 1.8 million people to 341,784,857. In 2024, the U.S. population grew by 3.2 million people, with 2.7 million coming from other countries.
Most states saw slower growth in 2025, even North Carolina, the nation’s fastest growing state at 1.5%. But that was slower than the 1.8% increase it recorded in 2024. Population declined in five states: California, Hawaii, New Mexico, Vermont and West Virginia.
Colorado’s population growth has been slowing for several years. Housing affordability, the relatively higher cost of living and state policies also may have played a role in encouraging newcomers to move here and long-timers to leave.
But there are signs that the net loss of people leaving Colorado last year is not the start of “significant out-migration from Colorado,” said Bill Craighead, program director at the UCCS Economic Forum in Colorado Springs.
He pointed to the state’s unemployment rate, which had been higher than the U.S. when the population data was tracked. It’s been lower since August and continued the downward trend in December. Housing prices have flattened. Apartment vacancies are up and rents are falling due to a rapid increase in the housing supply from new construction in the last three years.
“We are seeing some gradual improvements in housing affordability, which is a barrier to people moving here … since we think of affordability as cost relative to income and incomes gradually rise over time,” Craighead said in an email.
“That said,” he added, “this is a reminder that Colorado has historically relied on people — especially college graduates — moving from other states in their late 20s and early 30s. With the national population growing so slowly and also aging, the pool of people that Colorado has drawn from isn’t going to be growing the way it was and looks like it will even start to shrink.”