Never mind Beverly Hills 90210. Residents of four communities strung out along Route 7 in Loudoun County have their own statement to make. But the question is, do they want to live in Potomac Falls 20165 or Sterling 20165?

What's the difference? Plenty, some say, noting that Potomac Falls conjures up an image--of rushing river water and the grazing horses and large manicured lawns of, say, Potomac, Md.--while Sterling conjures up . . . well, just Sterling.

The social gulf in eastern Loudoun, where Route 7 neatly divides the older neighborhoods of Sterling and Sterling Park on the south from newer subdivisions to the north, has recently widened with the opening of a new post office in Cascades, on the newer side of the road.

With the new post office, those living north of Route 7 in the 20165 Zip code now have the choice of giving themselves either a Potomac Falls address or one in Sterling. To some of the thousands of upwardly mobile middle-class newcomers rushing to fill the new homes in eastern Loudoun, the name Potomac Falls signifies everything that Sterling, a 1950s subdivision beset by sagging property values, is not.

For some, the matter is a cause of postal customer angst.

"I'm torn between the two, personally," said Pamela K. Brown, 43, who was told by her builder when she moved to Cascades in July that her address was Potomac Falls. "I think it's a way for people on this side of the road to distinguish themselves from people on the other side because the houses over there don't cost as much."

Edgar Wotring, 49 and a 10-year resident of Sterling Park, said he wouldn't switch even if he could. "I will always use Sterling," said Wotring. "I don't necessarily find it [Potomac Falls] offensive, I just don't want to use it."

Oddly enough, the name-game dilemma began as an attempt to forge community spirit among the look-alike subdivisions of eastern Loudoun. When the U.S. Postal Service announced plans two years ago to build a branch of the Sterling post office in Cascades, residents along the northern side of the Route 7 corridor decided they wanted to stamp their branch with its own identity and call it something other than Sterling, a name with which the 8,000 or so residents of Cascades, Countryside, Broad Run Farms and Potomac Woods did not identify.

Potomac Falls, on the other hand, offered a connection to the nearby Potomac River and a high school being built in the community at the time.

Postal officials approved the two-address option after receiving favorable nods from the U.S. Board on Geographic Names, which will use Potomac Falls in mapping, and the county Board of Supervisors, which mustered three votes in favor (with five abstentions and one supervisor not voting).

In Sterling and Sterling Park, hurt feelings linger. "We are a fairly contiguous community and we have a lot of common concerns," said Linda Conti-White, a leader of the Sterling Foundation, a nonprofit volunteer group. "So I have mixed feelings about it."

Over on the north side of the highway, Potomac Falls pride is growing. "When you say Potomac Falls, people think of the new area that's just come up with all the Internet companies and the nice houses," said Donna Ching, a federal budget officer living there. "It definitely costs a lot more than Sterling. It's like two separate communities."