WASHINGTON >> America’s population growth has declined to its slowest rate since the Great Depression, the Census Bureau said today, while the nation’s political center of gravity keeps shifting further to the Republican-led South and West. Texas, Florida and other Sun Belt states are gaining congressional seats as chillier climes like New York and Ohio lose them.

Altogether, the U.S. population rose to 331,449,281 last year, the Census Bureau said, a 7.4% increase that was the second-lowest ever. Experts say that paltry pace reflects the combination of an aging population, slowing immigration and the scars of the Great Recession, which led many young adults to delay marriage and starting families.

The new allocation of congressional seats came in the U.S. Census Bureau’s first release of data from a 2020 headcount. The numbers generally chart familiar American migration patterns but also confirm one historic marker: For the first time in 170 years of statehood, California is losing a congressional seat, a result of slowed migration to the nation’s most populous state, which was once a symbol of the country’s expansive frontier.

The census release marks the official beginning of the once-a-decade redistricting battles. The numbers released today, along with more detailed data expected later this year, will be used by state legislatures or independent commissions to redraw political maps to account for shifts in population.

Those shifts have largely been westward. Colorado, Montana and Oregon all added residents and gained seats. Texas was the biggest winner — the second-most populous state added two congressional seats, while Florida and North Carolina gained one. States losing seats included Illinois, Michigan, Pennsylvania and West Virginia.

Neighborhood counts mattered. Census said if New York had counted 89 more residents, the state would have kept its seat and Minnesota would have lost one.

The reshuffling of the congressional map moved seats from blue states to red ones, giving Republicans a clear, immediate advantage. The party will have complete control of drawing the congressional maps in Texas, Florida and North Carolina — states that are adding four seats.

In contrast, though Democrats control the process in Oregon, Democratic lawmakers there have agreed to give Republicans an equal say in redistricting in exchange for a commitment to stop blocking bills. In Democratic Colorado, a nonpartisan commission will draw the lines, meaning the party won’t have total control in a single expanding state’s redistricting.

It’s been a bumpy road getting this far. The 2020 census faced a once-in-a-century coronavirus pandemic, wildfires, hurricanes, allegations of political interference with the Trump administration’s failed effort to add a citizenship question, fluctuating deadlines and lawsuits.

The new congressional numbers contained some surprises. Though Texas and Florida grew, the census count had them each gaining one fewer seat than expected. Arizona, another fast-growing state that demographers considered a sure bet to pick up a new seat, failed to get one. All three states have large Latino populations that represent about half their growth, and the count could be an early sign that Hispanics shied away from participating in the Trump administration’s count.

The overall numbers do confirm what demographers have long warned — that the country’s growth is stalling out. Many had expected growth to come in even below the 1930s levels given the long hangover of the Great Recession and the drying up of immigration, which came to a virtual halt during last year’s pandemic.

William Frey, a demographer at the Brookings Institution in Washington, D.C., warned that even a recovering economy may not change the trend with the population aging rapidly and immigration contentious. “Unlike the Great Depression, it’s part of a process where we’re likely to keep having slow growth,” Frey said.

Meanwhile, Americans continue to move to GOP-run states. For now, that shift provides the Republicans with the opportunity to shape new congressional districts to maximize the influence of their voters and have a major advantage in upcoming elections — possibly enough to win back control of the U.S. House.

But in the long term, it’s not clear the migration is good news for Republicans. Many of the fastest growing states are increasingly competitive political battlegrounds where the new arrivals — including many young people and people of color — could at some point give Democrats an edge.

“What’s happening is growth in Sunbelt states that are trending Democratic or will soon trend Democratic,” Frey said.

That means Republicans may be limited in how many favorable seats they can draw as Democrats move to their territory.

“It’s going to be harder and harder for the Texas Legislature to gerrymander advantageous congressional districts” for Republicans, said William Fulton, director of the Kinder Institute for Urban Research at Rice University in Houston. “Texas hasn’t flipped blue yet as a state, but the blue population centers are growing really fast.”

Fulton, who moved to Texas from California, said his new home has become “the new California — the big state that’s adding a lot of population.” He believes California risks becoming the new Northeast — which he characterized as a stagnant, crowded area that retains wealth and intellectual clout but loses innovators to more promising places.

Despite California’s slow growth, the state still has 10 million more residents than Texas.

North Carolina and Texas, Fulton said, are positioned to become the intellectual powerhouses of the new economy, as the South has snatched away major manufacturing industries like automobiles from the Rust Belt. “We are 10-20 years away from the South and the West being truly dominant in American culture and American society,” Fulton said.

But population booms also bring new burdens, like increased traffic, rising home prices and strains on an infrastructure already grappling with climate change — vividly illustrated when the Texas power grid failed in the winter storms of February.

The pattern outlined in the the Census data was one started in the 1930s with the invention of modern air-conditioning and has been steady since then, according to experts. The only change in the pattern was the halt in California’s growth.

That has happened as home prices have soared in California, contributing to a steady stream of residents leaving for other Western states. Those relocations helped turn Colorado and Nevada into Democratic states and made Arizona competitive.

“That’s the California exodus, blue state immigrants,” Frey said. “Californians are taking their votes and moving to other places.”

It’s not just Californians who are moving. Brad Baskin and his wife, Janie, moved from the Chicago suburbs to Orlando, Florida, three years ago to be closer to their daughter, son-in-law and grandchildren. Janie Baskin is a registered Democrat, while Brad Baskin hasn’t registered a party affiliation but was turned off by Trump.

The political views they have encountered in Florida have been a bit jarring, going from a state overwhelmingly dominated by Democrats to one where Republicans are in control at the state level, though Democrats control most municipal offices in the county that is home to Orlando.

Baskin, a photographer, said he recently made head shots for a client who told him, “It’s OK for you guys to move down here, but leave your liberal views up there.”

The power shift is also being driven by Hispanics. Over the decade, Hispanics accounted for around half of the growth in Arizona, Florida and Texas, according to figures from the American Community Survey, a Census Bureau program separate from the decennial census.

The state population figures known as the apportionment count determine not only political power but the distribution of $1.5 trillion in federal spending each year.

The legal deadline for turning in the apportionment numbers was Dec. 31, but the Census Bureau pushed back that date to April because of challenges caused by the pandemic and the need for more time to correct not-unexpected irregularities.

More detailed figures will be released later this year showing populations by race, Hispanic origin, gender and housing at geographic levels as small as neighborhoods. This redistricting data will be used for redrawing precise congressional and legislative districts.