While rapid growth in the greater Charleston area has led to elementary schools that are bursting with children, the real face of population gains in South Carolina is an aging one.

Mirroring national trends, the number people at least 65 years old has been increasing quickly in the Palmetto State, and the number of those at least 85 is likewise rising fast, according to a Census Bureau report released this morning.

The tri-county area, with colleges and an economy that's attracted working-age adults, skews a little younger than the state as a whole, but across South Carolina nearly two-thirds of the population gains from mid-2010 to mid-2013 involved the 65-plus group.

Retirees moving South are part of the story, but the big picture is that in South Carolina and across the nation, the large post-World War II baby boom generation is advancing in years.

"That's why senior centers are so important, and we've been fortunate in this area to have wonderful senior centers that people can access," said Stephanie Blunt, executive director of the Trident Area Agency on Aging.

Ed Ledford, 78, has lived in the Charleston area since 1965, where he coached cross-country at College of Charleston and worked as a social worker. He goes to the Lowcountry Senior Center on James Island almost every day, where he participates in an investment group and takes clogging, line dancing and hooping classes.

"You really do form friends here, and you do a lot of things you wouldn't otherwise try," the Folly Beach resident said. Ledford, a former Wake Forest University cross-country runner, also uses the gym and track to stay active.

Ron Alexander is 69, but don't call him retired. He moved to James Island from Upstate South Carolina in November, and says he's starting his fourth career as a writer and storyteller. Previously, he served in the Army and was a clinical pathologist.

"I'm not retired, I'm wired," he said.

Alexander sailed while he was a student at Clemson, and now works with Vets on Deck, a therapeutic sailing program for military veterans.

The growth of the 65-plus population can be harder to see than rising numbers of children and young adults, because the older residents don't require new school construction and may not contribute to rush-hour traffic. But theirs are the numbers that are rising fast.

Across the U.S. the number of residents at least 65 years old jumped 3.6 percent in a single year, 2012 to 2013, while the under-65 population climbed less than one-third of one percent, the census data shows.

It's a long-term demographic trend that's playing a role in everything from anticipated job growth for nurses to financial problems facing the Social Security and Medicare systems.

In South Carolina, there were an estimated 78,726 people at least 85 years old in mid-2013, which is 7,274 more than there were three years earlier. During that same time, the number of residents under age 17 increased by just 3,799.

Reach David Slade at 937-5552.

Editor's note: A previous version of this story misstated Ron Alexander's military service and sailing affiliation with Clemson.