It’s not just the Northeast that’s confronting the challenges of an increasingly older population: In Iowa, the amber waves of grain, too, are starting to look a little grayer.

As Iowa lawmakers plan future spending on priorities from health care to urban planning, they find themselves confronting more urbanization and a rising elderly population. And the changes are only speeding up.

Iowa is one of eight states where the population hasn’t doubled over the last century. It’s the only state that hasn’t grown by at least 50 percent in the same time, said Tim Albrecht, a spokesman for Gov. Terry Branstad (R). Iowa had 2.2 million residents in 1900; the 2010 Census estimated the state had 3 million residents.

By contrast, the United States as a whole grew from about 76 million people in 1900 to about 313 million today.

Younger Iowans have rapidly been moving away from the rural counties that produce the billions of dollars of the state’s agricultural products, in favor of urban areas and other states. Two-thirds of Iowa’s counties lost population over the last decade, according to Census data, while urban counties such as Polk, Dallas, Story, Madison and Warren — the five counties that include and surround Des Moines — and Linn and Johnson counties, which include Cedar Rapids and Iowa City, posted the biggest increases.

The flood of younger Iowans away from rural counties is sending the median ages in those areas through the roof. Already, Monona County, which lies along the Missouri River north of Omaha,  has more residents over age 65 than it does residents under age. By 2040, Albrecht said, state demographers believe 60 of the state’s 99 counties will fall into that category (click here for a pdf of where Iowa grew and shrank between 2000 and 2010).

Median age of Iowa counties:

“The demographics of our state and how and where we are growing are critically important when tackling policy issues like health care reform, mental health care funding and the long-term sustainability and access to programs in aging counties in our state,” Albrecht said.

We wrote last week on the challenges that states with rising median ages face, with older Americans consuming more social service resources while contributing less to the tax base. The key, advisers to several governors told us, is a fresh approach to keeping younger residents, in hopes of broadening the tax base.