The U.S. foreign-born population has risen to its highest level since 1920, with 13% of all those living in the nation in 2010 having been born elsewhere, a new report from the Census Bureau shows.

Forty million of those residing in the U.S. in 2010 were born in other countries, up from 31 million, or 11% of the total, a decade earlier. The foreign-born share of the population dropped between 1920 and 1970, hitting a low of 4.7% in 1970, before rising again for several decades.

But that growth has slowed in recent years as immigration has dropped, census officials said Thursday. Most of the recent increase in the foreign-born population came between 2000 and 2006, said Elizabeth M. Grieco, chief of the bureau’s foreign-born population branch.

California is home to the lion’sshare of the foreign-born population, with 1 in 4 residing in the Golden State, the new report shows. Twenty-seven percent of the state’s population of 37 million in 2010 was born abroad, up from 26% in 2000.

Three other big states, New York, Texas and Florida, accounted for a third of the nation’s foreign-born population, with New York having the second-highest total at 11%. West Virginia had the smallest percentage, with just 1% born outside the U.S.

The new report draws on the 2010 American Community Survey, an annual poll of 3 million U.S. households.

The report details many characteristics of the foreign-born population, showing that on average, foreign-born households are larger than those of people born in this country, have more children younger than 18 and are more likely to include three generations or more living under one roof.

The foreign-born were more likely to be employed than native-born Americans, the study showed. Sixty-eight percent of the foreign-born population age 16 or older were working in 2010, compared with 64% of those born in the U.S. And 79% of foreign-born men were in the labor force, compared to 68% of native-born men; in contrast, 60% of U.S.-born women were employed, compared with 57% of foreign-born women.

But people born elsewhere were less likely than those born in this country to have health insurance and more likely to be living below the poverty line. Among regions of birth, the poverty rate was highest for the U.S. foreign-born population from Latin America and from Africa.

More than half of the nation’s foreign-born people arrived from Latin America and the Caribbean, with most of those from Mexico, the report showed. More than a quarter of the total came to the U.S. from Asia, with about 12% from Europe, 4% from Africa and smaller percentages from other regions.

Those who arrived in the U.S. since 2005 were more likely than other immigrants to live outside such traditional “gateway” states as California, New York and Texas, the Census Bureau said in another recent study. Although the gateway states still accounted for the majority of the newly arrived, many recent immigrants were settling in states with smaller foreign-born populations, including Louisiana, Mississippi, Wyoming and the Dakotas.

The annual American Community Survey took the place of the long-form decennial census in 2010 and is used to help distribute $450 billion in annual federal funds. But a bill moving through Congress is seeking to eliminate its funding, with the bill’s Republican sponsors arguing that the survey is unconstitutional and an invasion of privacy.

The Republican-controlled House voted 232 to 190 this week along party lines to cut all funding for the survey in 2013.The Senate, where Democrats hold a majority, has not acted on the bill.

rebecca.trounson@latimes.com