LOCATION -- On the Potomac River, across and slightly upstream from Mount Vernon, just north of the Charles County line and west of Indian Head Highway.

RACIAL MAKEUP -- Tantallon is about one-third black and two-thirds white with an increasing Asian population.

DESCRIPTION -- Very large, typically brick, custom-built houses, many with double-door main entries and two-story-high foyers, on lots of a quarter acre to a half acre. Potomac Landing Elementary School is highly rated. Fort Washington Forest Elementary School opened this year as a magnet school emphasizing science and mathematics. There is a strong citizen association with strict architectural controls. The neighborhood includes Tantallon Country Club, two marinas -- Tantallon and Fort Washington -- and Fort Washington National Park.

COST OF HOUSES -- Most common: $250,000. Typical range: $185,000 to $350,000. Waterfront houses can cost $750,000 or more. Houses near the fairways of the Tantallon Country Club can cost $500,000. A vacant waterfront half-acre lot is $125,000.

POPULATION -- Numerous doctors, lawyers, other professionals and high-ranking military officers.

SAMPLE FAMILY -- Major Riddick, 37, is the budget director of Prince George's County. His wife Manerva, 39, is the general manager of Metrovision, the cable firm that has the franchise for the southern end of Prince George's County. Their daughter, Myrica, 7, is enrolled in private school. Their 5,600-square-foot house has two living rooms; two home offices, one with a computer; a carpeted and mirrored exercise room, and a sauna. They estimate that it is worth $300,000.