LOS ANGELES — For the first time in the modern era, non-Hispanic whites are officially a minority in California, amounting to a little less than half the population of the most populous state, compared with nearly three-quarters only a decade ago, according to new census figures.

Hispanic residents now make up nearly one-third of the state's population.

The change was long expected, the result of high Hispanic birthrates and decades of immigration but combined with a 43 percent increase in the state's Asian population, it confirmed California's status as the nation's most diverse big state and was viewed as a harbinger of changes in other populous states like Florida, New York and Texas.

California easily remained the most populous state, home to nearly one in 8 Americans, and its highest rates of population growth came in the inland valleys least associated with swimming pools and movie stars. The fastest-growing county was Placer, a picturesque area in the Sierra Nevada foothills northeast of Sacramento that was the scene of the gold rush in 1849 and that recently became a commuter haven; its population grew 42 percent the past decade.

Over all, California gained slightly less than 3 million people, for a total of 33.9 million, compared with adjusted figures from the 1990 Census, a growth rate of a little less than 10 percent. The state's increase in people was more than the individual populations of about half the states in the union.

More than 43 percent of Californians younger than 18 are now Hispanic, compared with about 35 percent a decade ago, the figures released Thursday show.

Hispanic is a demographic group, not a race, and Hispanics may be of any race.

"The Anglo hegemony was only an intermittent phase in California's arc of identity, extending from the arrival of the Spanish," said Kevin Starr, the state librarian and author of cultural histories of the state.

"The Hispanic nature of California has been there all along, and it was temporarily swamped between the 1880s and the 1960s," Starr said, "but that was an aberration. This is a reassertion of the intrinsic demographic DNA of the longer pattern, which is part of a California-Mexico continuum."

The state's black population declined by 3 percent, to 2.3 million when some of the residents who listed themselves as mixed-race are counted as black, while the black population of the most populous county, Los Angeles, declined by 12 percent, to 920,899.

The state's white population declined, too, by about 8 percent over the decade. Because that figure was so high, blacks maintained almost the same percentage of the population, roughly 7 percent, as in 1990.

A comparison of census data by The New York Times used adjusted figures for 1990 provided by the United States Census Bureau that added an estimate of residents, mostly members of minorities, who were believed to have been missed in that count. The figures for 2000 have not been adjusted for those people, but last year's census is considered more accurate.

The national increase in the Hispanic population was 58 percent, significantly higher than the 33 percent increase in California. But the number of new Hispanic residents here dwarfs the number in other states; nearly a third of all Hispanics in the nation live in the Golden State.

"California certainly represents what many states are moving toward," said Dr. Paul Ong, director of the Lewis Center for Regional Policy Studies and a professor of urban planning at the University of California at Los Angeles.

"I don't think most states will end up at the same level of diversity," Dr. Ong said. "The truth of the matter is the rest of the country is going in this direction, but it won't become this, in the same way that New York at the beginning of the last century represented an important trend, but the rest of the country didn't become New York."

Of California's 2.7 million new Hispanic residents, the majority were the result of births outpacing deaths among Hispanic residents, state demographers said. Less than one-fifth of the growth was from immigration, recent state figures indicated. As a jurisdiction where non-Hispanic whites are in the minority, California joins New Mexico, Hawaii and the District of Columbia.

By contrast, most of the growth in the Asian population was because of immigration. Asians account for almost 12 percent of the state's population, or 3.9 million residents, compared with 9 percent a decade ago. Some of the largest percentage increases for this group, too, came in the cluster of north-central counties known as the Gold Country, where Chinese immigrants once flocked to the pan for gold.

With coastal California already heavily settled from San Diego to San Luis Obispo, and with many localities passing ordinances to limit growth or suburban sprawl, it was hardly surprising that some of the highest rates of population growth came in counties like Riverside and San Bernardino, the so-called Inland Empire east of Los Angeles, and in counties of the Central Valley, where farmland is increasingly giving way to affordable tract housing. Even in those areas, the Hispanic population rose, though not as swiftly.

The cross-cutting demographic trends of coastal urban populations that are increasingly Hispanic and Asian, groups that in recent years have trended strongly Democratic, and more white, moderate-to-conservative residents inland, are posing new challenges for politicians.

"It means that either party to be successful statewide has to be able to appeal to the moderate to conservative voters that seem to be constituting much of the growth in California's inland areas," said Garry South, chief political adviser to Gov. Gray Davis, a Democrat. "And Republicans are not going to be successful statewide unless they can come up with some way to rebuild and repair the damage they've done among Asian and Latino voters with the anti-immigration crusades of the 1990s."