The state’s No. 2 county, long eclipsed by No. 1, is catching up on one big bragging-rights metric: rate of growth.

Ramsey County in this decade is managing to do something it hasn’t done since at least World War II — add residents at a rate nearly identical to that of Hennepin County, its much bigger neighbor.

Moreover, forecasts call for that trend to continue for decades. A key reason, according to demographers, is Ramsey County’s status as a destination for immigrants, often youthful and ready to have bigger families than U.S. natives.

“I think I shocked some city staff in St. Paul not long ago when they asked me about a need to prepare for an aging population,” State Demographer Susan Brower said. “And my response was, ‘You know, you’re pretty young here!’ They’d heard about the Age Wave and thought it applies to all.”

Estimates for 2015 put Hennepin County’s population at 1.2 million, and Ramsey County’s at 534,000. But the rate of growth for the two counties so far this decade is only fractionally different — Hennepin up 6.9 percent, Ramsey up 6.3 percent — according to updates this spring.

Throughout that time, Ramsey has led in persons per household.

Both counties’ immigrant share rose from 2005 to 2015, but Ramsey grew more — from 11.3 percent foreign-born to 15.3 percent — and claimed a bigger share than Hennepin.

Youth and room to grow

Ramsey County, and notably St. Paul, is younger than Hennepin County. Ramsey’s median age is 34.8, versus 36.2 for Hennepin.

Mindee Kastelic, interim president of the St. Paul Area Chamber of Commerce, said businesses cherish a young labor force as baby boomers retire. Ramsey has a population that can plug those employment gaps.

Adolph Mottey and his nephew Wilfried Woumadi, immigrants from the west African nation of Togo, proudly showed off their communal garden plots in Roseville Tuesday afternoon and said that between them, they brought five children.

“My three are now IT engineers and a medical doctor,” said Mottey, who arrived in 2004 when the kids were teenagers. “His two are younger, but still contributing to the population of Ramsey County!”

Both men agreed with Mottey’s assessment, as symbolized by Rice Street Gardens, 260 plots near Larpenteur Avenue that mingle the work of Hmong, Nepali, Africans and others: “I like Ramsey County. I don’t know why, it’s just cool. People have a good heart.”

Kumar Tamang, from Nepal, gardening at the other end of the vast space, added that a place that attracts immigrants will continue to draw them as people settle with family and fellow countrymen. “It’s language, it’s family, it’s staying close together in a new place.”

In truth, demographer Brower said, both central cities are receiving zones for young immigrants.

“They are moving to places with affordable housing, transit, things they need to establish themselves,” she said.

But Hennepin is a more suburban county than Ramsey, where St. Paul comprises one-third of the county’s area. So Ramsey ends up with more of the youthfulness and potential to grow.

Ramsey County also has a couple unusual on-the-ground opportunities that could add several thousand households in just a few hundred acres: the former ammunition plant in Arden Hills, owned and cleared by the county, and the old Ford plant site in St. Paul’s Highland Park neighborhood.

The two mega-development sites have emerged at a time when communities across the country are moving toward high-density, walkable urban villages.

‘The big wild card’

Ironically, it’s also a time when Ramsey County and the whole east metro area are uneasy about their growth prospects, as revealed in economic development efforts with names like Accelerate Ramsey and East Metro Strong.

Historically, the gap between the growth rates in Hennepin and Ramsey counties has been large. Although the two have tended to move in sync, Hennepin grew by 10 percent in the 1980s, compared with Ramsey’s 6 percent.

As recently as the first decade of this century, Ramsey was the only metro county to lose population. At times since the 1940s, Hennepin’s growth has been far more robust than Ramsey’s; even today Hennepin has a lot more room to grow, with plenty of farm fields left to be occupied, while the smaller Ramsey is practically fully developed.

Word that forecasts now call for Ramsey’s growth to equal Hennepin’s “is certainly news to me but not totally surprising news,” said Marie Ellis, director of public affairs for the St. Paul Area Chamber of Commerce. “The east metro has done a lot to position itself for growth.”

However, demographers caution that forecasts guarantee nothing — especially the outcome of a volatile factor like immigration at a time when the attitude towards its costs and benefits has changed in Washington, D.C.

“That’s the big wild card here,” said Megan Dayton, senior projections officer for the State Demographer’s office.