Horry County was the third-fastest growing county in the state during the past decade with 37 percent growth.
The surge was led by bedroom communities such as Carolina Forest, which quintupled in population, according to data released by the U.S. Census Bureau on Wednesday. The county's growth rate is slightly higher than it was between 1990 and 2000, when Horry County swelled by 36.5 percent.
Those numbers should come as no surprise to longtime county residents James Johnson and Sommar Adams, who marvel at how their Carolina Forest community barely existed a decade ago.
"It is kind of weird ... there used to be nothing here," said Johnson, 34, originally from Atlantic Beach. "It used to be nothing but woods."
Georgetown County grew at a much slower rate in the past decade, only seeing a single-digit increase in population. A few oceanfront and rural census tracts along the Grand Strand lost population.
Although officials and residents said they weren't surprised by the amount of growth, the census gives the first concrete picture of the Grand Strand's rapid growth since 2000.
"I don't think that the numbers are going to be a surprise to the people who lived here," said Janet Carter, Horry County Planning and Zoning director. "We've seen a tremendous number of subdivisions that have sprung up."
Horry County's population rose from 196,629 in 2000 to 269,291 in 2010, and only trailed Dorchester and York counties for highest growth rate. Overall, South Carolina's population grew 15.3 percent.
Horry County Council members said they expected at least 35 percent growth, and the communities and neighborhoods that grew the most were in line with assumptions, District 3 Councilman Marion Foxworth said.
The county is now the fifth most populous in the state, surpassing Lexington County. Greenville County is the most populous county in the state with 451,225 residents.
Coastal, urban and suburban counties in the state generally grew, but several rural counties lost population.
Georgetown County grew at a slower rate than Horry, increasing 7.8 percent to 60,158 people from 55,797 in 2000.
Bedroom communities - areas that are mostly residential - grew the fastest, with the census tract containing Carolina Forest experiencing population growth of 506 percent.
The Forestbrook neighborhood more than doubled its population with 125 percent growth and the Burgess area grew 87 percent. That trend also emerged in Georgetown County, where the Waccamaw Neck area - including Murrells Inlet and Pawleys Island - grew the fastest.
Most people who move to the area, whether working or retired, want affordable homes. But those are mostly located inland, said Rob Salvino, a research economist at Coastal Carolina University.
"We have this misconception that everybody comes to Myrtle Beach and lives on the water, but that's not the case." Salvino said.
That explains the population boom in Carolina Forest from 3,338 residents to more than 20,000 in the past 10 years, he said.
Some coastal areas lost population, led by the census tract containing the area between U.S. 17 Business and the beach in Garden City, which saw a 15.5 percent dip. The population of an oceanfront census tract from 17th Avenue North in Surfside Beach to Fourth Avenue South in Myrtle Beach shrank 10.6 percent.
Rural areas in Georgetown County mostly lost population, as did the census tract containing the city of Georgetown's downtown area, which lost roughly 400 residents.
S.C. Rep. Kevin Ryan, who represents almost all of the Waccamaw Neck area, which grew more than 30 percent, said the numbers speak for themselves.
"It's gone from a quiet community to a place a ton of people want to go to," Ryan said
The shrinking population in downtown Georgetown is likely the result of the steel mill closing, Ryan said. The mill closed in June 2009 and reopened in January, but now employs fewer workers.
The city of Myrtle Beach grew 19.1 percent to 27,109 and is the 14th most populous incorporated place in the state.
Myrtle Beach Mayor John Rhodes said he thought the city might grow more, but the growth is nevertheless good for the area.
"It means it's a very popular place and it's one where we're having people moving in," he said.
The growth hasn't put a strain on city services and won't require any changes because the city has been keeping up with new residents as they move in, he said.
Horry County Schools have already built River Oaks Elementary School to cope with Carolina Forest's growth, said Joe Burch, who coordinates planning for the district. The school is scheduled to open in August 2012. No other building is planned yet, but the district will look at the census to determine how to resolve disparities between different areas.
Georgetown County Schools grew by about 100 students this year but lost about 1,000 students during the three previous years, mostly in rural areas, Superintendent Randy Dozier said. Waccamaw Neck was the only area of the county that showed strong growth. A new intermediate school has opened there and the high school is expanding.
Whether the growth revealed in the census data is good or bad news is a matter of whether people think the area is already overpopulated, Salvino said.
"If you're talking about economic growth and demand...I would say it's good," said Salvino. "But other people would say they didn't want any more people coming."
Staff reporters Adva Saldinger, Gina Vasselli, Brad Dickerson and Vicki Grooms contributed to this report.