The newly released figures show that the nation's Hispanic population grew by 1.4 million in 2007 to reach 45.5 million people, or 15.1 percent of the total U.S. population of 301.6 million. African-Americans ranked as the second-largest minority group at 40.7 million people.

Latino population will double from 15 percent today to 30 percent by 2050.

The census figures showed a slight drop in immigration to the United States by Hispanics from July 1, 2006, to July 1 vs. the previous 12-month period. That suggests the U.S. economic slowdown might have had some impact on immigration. For nearly a decade, U.S. births have accounted for a far greater share of the growth in the Hispanic population than immigration.

Nonetheless, many researchers warn that the higher-than-average poverty rate of U.S.-born Latino children and the fact that many are raised by immigrant parents pose particular challenges to their education and integration.

"Based on what we know, many in this population may not be growing up speaking English in their homes," said Margie McHugh, co-director of the National Center on Immigrant Integration Policy at the Migration Policy Institute in Washington. In a recent study, McHugh found that 75 percent of limited-English-proficient students in Los Angeles County elementary schools were born in the United States. MORE