WASHINGTON, March 7 — The Hispanic population in the United States has grown by more than 60 percent in the last decade, pulling it into rough parity with blacks as the largest minority, early data from the 2000 census show.

The new data carry broad political and cultural implications for a nation undergoing major demographic shifts. In this case, demographers said, the soaring Hispanic population was driven largely by waves of new immigrants, legal and illegal, as well as by an improved ability by census takers to count this group.

The figures showed that the number of Hispanic people, who have Spanish-speaking ancestry but may belong to any race, including black, soared to 35.3 million from the 22.4 million recorded in 1990. The 2000 total was about three million more than the Census Bureau had previously estimated, a difference demographers attributed to illegal immigrants.

In contrast, the number of blacks rose by about 16 percent to 34.7 million from the 30 million counted in the 1990 census.

"This is fairly significant because it spells the transition of the Latino population toward becoming the largest minority in the country," said Representative Silvestre Reyes, Democrat of Texas, who heads the Congressional Hispanic Caucus.

The growing Hispanic population is a major reason that for the first time since the early 1930's, one of every 10 Americans is foreign born.

Demographers have long anticipated that Hispanics would supplant blacks as the nation's largest minority, but earlier census reports had forecast that this would happen by 2005.

The new information, which represents some of the first details to emerge from the count last year, was included as background tables in a public report issued last week and was first reported today by The Washington Post.

While Hispanics are still concentrated in the Southwest, California, Florida and New York, new immigrants from Mexico and Central America have moved to states like North Carolina, Georgia and Iowa, where the Hispanic population was almost nonexistent a decade ago.

Hispanics have become a mainstay in many low-paying, labor-intensive industries. In Atlanta and Memphis, they dominate the construction and landscaping trades. In eastern North Carolina, they process hogs. In Arkansas, they pluck chickens.

The new census figures also disclosed that about one in 20 residents who consider themselves black — about 1.8 million people — checked at least one other race in the census, the first national count to allow that option.

People filling out the census form were asked to identify themselves by race as white, black, Asian, American Indian or Alaska native, native Hawaiian or other Pacific islander, or other race. They could check one or more boxes.

The trend of people who consider themselves black to identify with at least one other race is especially true among of those under age 18. Eight percent of that group identified themselves as black and belonging to another race, compared with 2.3 percent of blacks over age 50 who said they belonged to another race.

"It's a reflection of a very rapid increase in interracial marriages and the fact that many younger blacks are looking back in their ancestry beyond their parents," said Jeffrey S. Passel, a demographer with the Urban Institute, a social policy research organization.

Mr. Passel warned that while this data might provide a better picture of the way black people view themselves, it might actually hamper the way other people view blacks.

"Down the road, this will lead to complications in the use of the data, and will ultimately muddy the waters of measuring and remedying discrimination," said Mr. Passel, who said he stumbled across the figures on Hispanics and blacks while perusing the Census Bureau's Web site.

The Census Bureau is expected to release early next week a comprehensive analysis of the complex American racial makeup, including a breakdown of black and nonblack Hispanics.

Even as census documents begin to paint a portrait of the country's population, census officials acknowledged that 5.7 million people who could not be completely identified were added by statisticians to the census, based on a statistical portrait of their neighborhoods. That number of people is a sharp jump from the 2.2 million individuals who were statistically added in the 1990 census.

John Thompson, director of the 2000 Decennial Census, said the bureau did not yet know why three times as many hard-to-reach people had been statistically added to the 2000 census than had been the case 10 years ago.

"We really want to understand it and go back and learn about it," Mr. Thompson said, speaking of large number. "We really don't know about it at the present time."

The growing Hispanic population has sent ripples through every sector of American society and culture, from pop music and food to political campaigns and corporate marketing.

But demographers and political analysts issued several caveats about the political impact of the new census data.

"Hispanic" is a catch-all term designed to cover a disparate array of people from various nationalities, from liberal Puerto Ricans in New York to conservative Cubans in Miami, who do not always have common interests.

"It's hard to really know how strong the Hispanic identity is among all these groups," said Eugene P. Ericksen, professor of sociology and statistics at Temple University.

Moreover, a large proportion of the new Latino residents are immigrants, often with young children, who are not yet citizens, and thus cannot vote. Clearly, though, politicians in both parties have aggressively courted Hispanic voters.

In his race last year, President Bush sought to attract Latino voters in part by using his Spanish-speaking nephew, George P. Bush, on the campaign trail and by speaking Spanish himself. He had mixed success.

Mr. Bush won 31 percent of the overall Hispanic vote in the 2000 elections. The election-day surveys of voters leaving polling places showed not only that national figure but also wide variations among the states.

For example, Mr. Bush won 49 percent of Latino voters in Florida and 43 percent in Texas, where he was the governor, but only 28 percent in California and 18 percent in New York, according to polls of people after they cast ballots.

Hispanic lawmakers on Capitol Hill have pledged more aggressive voter outreach efforts. Currently, Hispanics hold 21 seats in the House, compared with 39 seats held by blacks. As a result of the 2000 census, Nevada will pick up an additional House seat in the Las Vegas area, and Mr. Reyes said Democratic Hispanics have already identified a leading candidate for the position, Dario Herrera, a county commissioner.