Soaring unemployment has pushed California's poverty rate up for three straight years -- but nowhere higher than in Fresno County, according to new Census data.

The nearly 250,000 county residents living in poverty in 2010 gives Fresno County claim to the state's highest poverty rate, at 26.8%. Almost 70,000 more people lived in poverty last year than in 2007 when the recession began.

Statewide, 15.8% were impoverished, the census data show, up 3.4 percentage points from three years ago.

Several counties in the San Joaquin Valley were among the state's poorest, according to the data.

Experts attribute this to the region's weak economy and unskilled labor market -- made worse by the nation's economic slide.

Fresno County, though, has been particularly vulnerable to the bad times, said Alan Berube, a senior fellow at the Washington, D.C.-based Brookings Institution. The county's many pockets of concentrated poor have made it a harder place to turn around, he said.

"You've got these problems that compound in these very poor communities: bad housing, people staying inside because their neighborhood isn't safe. This makes it more difficult for people to get into a job and escape poverty," he said.

Fresno County ranked seventh in the state for poverty a year earlier, when the number of impoverished was 5.3 percentage points less.

Merced County, with its poverty rate remaining statistically unchanged at 23.1% in 2010, fell from the top spot to number four. Tulare County had the state's second-highest poverty rate, with 24.6% of its residents living in poverty last year.

Berube, whose research on poverty has focused on the Valley, said the housing boom of the mid-2000s brought jobs to the region, but only temporarily.

"The housing jobs aren't there now," he said, "And there's less of an agricultural base to fall back on. Everyone knows that agriculture has gotten more and more mechanized and requires fewer hands to produce the same amount of food."

Like many, Berube said the key to reducing poverty in Fresno County and other Valley communities is expanding the skills of the workforce and diversifying the economy.

Last month, Fresno County's unemployment stood at 15.7% while the state's rate was 11.7%.

The numbers released Tuesday by the U.S. Census Bureau are the first to detail poverty rates in 2010 for counties and school districts. The data help steer federal funding.

The federal poverty rate varies with family size and age, but for a typical household of four, the line was $22,113 in 2010.

The high number of poor in the Valley held true for the young, too.

In Fresno County, the poverty rate among school-aged children jumped from 27.1% in 2007 to 36.2% in 2010 -- also highest in the state.

Statewide, 20.8% of school-age children lived in poverty.

Education experts say poverty and its associated problems put an extra burden on educators, only making it harder for children to get the schooling they need to break out of poverty.

"When young people are struggling with a troubled home life and bad nutrition, that means the teacher in the classroom has to provide additional comfort and support and remediation," said Walt Buster, co-director of the Central Valley Educational Leadership Institute at California State University, Fresno.

Buster said providing these social services is a noble cause that teachers accept, but it can make concentrating on academics that much harder.

West Fresno Elementary School District, recently taken over by Washington Unified School District, had among the state's highest concentrations of poverty. About 57% of the student body was impoverished, according to the 2010 census data, the second-highest rate among California schools with more than 100 students.

At Fresno Unified School District, 44% lived in poverty.

Buster, whose job is to help create more successful schools, said poverty won't go away until children get a better education.

"If we're going to improve, " he said, "we need to see education as an investment."