If you want to chart the Lowcountry's rapid population growth since 2010, follow U.S. 278.
The highway cuts through the area's fastest-growing municipalities, according to new U.S. Census data released Thursday.
Between July 2010 and July 2014, the city of Hardeeville grew faster than any city in the state.
The town of Bluffton wasn't far behind, according to the data, which estimates population growth in U.S. cities during that period.
In the same time frame, the Town of Hilton Head Island reached a population milestone -- 40,000 permanent residents for the first time.
And the city of Beaufort and the town of Port Royal continued their characteristically steady growth, according to the new data.
"I think it's overall good news for everyone," Beaufort Mayor Billy Keyserling said of the statistics.
The new numbers show the most eye-popping population growth happening along U.S. 278.
The city of Hardeeville swelled by more than 50 percent -- about 1,700 people, according to the data.
Officials attribute the boom in part to growth in developments such as Sun City and Hilton Head Lakes.
"The numbers confirm what we've seen with regards to the number of permits our office issued in 2013 and 2014," said Hardeeville planning director Brana Snowden, who expects the city's population to rise above 5,000 by year's end.
The town of Bluffton held the top spot as Beaufort County's fastest-growing municipality, passing 15,000 residents for the first time.
It expanded by 13 percent -- about 1,800 people -- which was good for eighth-fastest in the state, the data show.
The driving force behind Bluffton's boom is home construction in places like Palmetto Bluff and Hampton Lake, officials have said.
Building permits issued for single-family homes jumped to 552 in 2014, almost 400 more than the town issued during the height of the Recession in 2009, according to town data.
Across the Hilton Head bridges -- where U.S. 278 becomes William Hilton Parkway -- the town experienced modest 7 percent growth between July 2010 and July 2014.
But it did reach the 40,000-resident milestone, becoming one of 10 South Carolina municipalities to reach that mark, according to data.
In northern Beaufort County, the city of Beaufort and town of Port Royal improved by 5 and 10 percent respectively.
Keyserling attributed the Beaufort increase to redevelopment downtown, as well as an influx of northerners who were finally able to sell their houses and move South.
He said new homes near Bladen and North streets have also attracted new residents.
"I think the migration of northerners in the last few years has come back," Keyserling said. "Is it where it was before (the Recession)? No. But we have activity going on."
The Beaufort County area overall is ranked among the nation's fastest growing metropolitan areas.
Here's what the population growth looks like by community:
Population increase: 5 percent
2014 - 13,130
2010 - 12,491
Population increase: 13 percent
2014 - 15,199
2010 - 13,408
Population increase: 53 percent
2014 - 4,789
2010 - 3,121
Hilton Head Island
Population increase: 7 percent
2014 - 40,039
2010 - 37,255
Population increase: 10 percent
2014 - 11,870
2010 - 10,752
Population increase: 1 percent
2014 - 4,076
2010 - 4,044
Follow reporter Dan Burley on Twitter at twitter.com/IPBG_Dan.