Their arrival added challenges and benefits. It put strains on school districts and emergency rooms. It provided ready workers for farms, high-tech industries, and landscapers. It raised tensions in places where ethnic groups clashed. But it brought vitality to communities where immigrants rehabbed abandoned houses and launched businesses.
With comparatively few native newcomers, "Philadelphia and Southeastern Pennsylvania have benefited from international migration," said Sue Copella, director of the Pennsylvania State Data Center in Harrisburg, the commonwealth's authority on population analysis. They come to Philadelphia through a reemerging gateway for immigration, she said, or "up from Baltimore and down from New York."
Pennsylvania's population grew 3.4 percent from 2000 to 2010, to 12,702,379. Absent Hispanic and Asian newcomers, however, it would not have grown at all.
Among arrivals spurring growth are Dominican immigrants moving from New York for cheaper housing and business opportunities; Mexicans joining friends and family in the established Hispanic enclaves of South Philadelphia, Norristown, and Kennett Square; Asian Indians joining well-established communities in Bensalem; and refugees from Cambodia, Burma, and Nepal being aided in resettlement by the Welcoming Center for New Pennsylvanians or Philadelphia's Nationalities Service Center.
"As far back as 2006, we saw academic studies that showed a substantial portion of workforce growth was attributable to immigrants," said Amanda Bergson-Shilcock, director of outreach for the Welcoming Center. "Those studies backed up what we were seeing on the ground in our work with work-authorized immigrants - people choosing the Philadelphia area as their destination."
The ranks of Hispanics grew 325,572 - a potent 82.6 percent since 2000. They are the state's "fastest-growing minority group," the Data Center reported Friday.
Having entered the state from the east, Hispanics have tended to settle in Pike, Monroe, and Luzerne Counties as well as Philadelphia and its surrounding counties. Asians and South Asians have clustered in Philadelphia, Upper Darby, and southern Bucks County.
From 2000 to 2010, Philadelphia added 58,683 people of Hispanic origin, which includes Puerto Ricans, who are U.S. citizens. The city added 28,402 Asians.
Delaware County grew by 8,169 Hispanics and 8,122 Asians, Bucks County by 12,777 Hispanics and 10,348 Asians, and Montgomery County by 18,933 Hispanics and 21,228 Asians.
Chester County experienced the region's sharpest population growth, 15.1 percent, and dramatic "percentage growth" in Hispanics and Asians. The addition of 16,377 Hispanics and 10,816 Asians to the county since 2000 drove their respective shares of the county's population to 6.5 percent and 3.9 percent.
Nelson Carrasquillo, director of CATA, the Farmworkers Support Committee, with offices in Kennett Square, said many of his group's members worked in the 120 mushroom farms that dot the countryside from Kennett to Reading.
He attributed Hispanic growth to a 1986 change in immigration law that gave amnesty to many undocumented Mexican farmworkers.
"People received papers and established permanent residence. Many became citizens" and applied to bring their wives and children here, Carrasquillo said.
"It took them a decade or more to save money and go through" the immigration paperwork process, he said, "but by the end of the '90s and into the 2000s, they began bringing in their families, and they still are."
The arrival of the wives from Mexico, Carrasquillo said, has resulted in more women working on the mushrooms farms, usually as packers.
As their children become voting-age citizens and move into other lines of work, he said, the political clout of Latinos is expanding.
Congress mandates a census every 10 years for the purpose of apportioning federal aid to the states and so the states can redraw political district lines to reflect population gains, losses, and changing demographics.
The release of the census for Pennsylvania starts the game of musical chairs by which the legislative leadership resketches the boundaries and jockeys for political advantage.
Because Pennsylvania grew at a slower rate than states in the South and West, it will lose one seat in the House of Representatives, dropping to 18.
Commuter access to New York City via I-80 supported dramatic growth in Monroe and Pike Counties. For people willing to drive a couple of hours, I-83 connects Baltimore and Washington to Franklin, Adams, York, and Lancaster Counties.
Still, said William Frey, a demographer with the Brookings Institution, most of the growth in Southeastern Pennsylvania is attributable to "new immigration waves" rolling and cresting on "the Northeast Corridor" between Washington and Boston.
Access to that string of metropolises "is going to be crucial for overall growth," he said, predicting that Southeastern Pennsylvania's growth will continue.
Contact staff writer Michael Matza at 215-854-2541, or firstname.lastname@example.org.
Inquirer staff writer Thomas Fitzgerald contributed to this article.
Town-by-town 2010 census data are at philly.com/census2010