Sam M. Walton, the down-home retailer who has earned millions by selling bargain-priced goods to rural America, is the nation's richest person with a fortune worth $2.8 billion, according to Forbes magazine.

In its annual list of the 400 richest people in America, Walton -- the chairman of Wal-Mart Stores based in Bentonville, Ark. -- replaced Gordon Peter Getty as the richest American.

Getty, whose fortune was valued at $4.1 billion last year, dropped to 15th place this year as a result of his agreement to divide the family oil trust with other family members. Forbes, in its Oct. 28 issue which will go on sale next week, placed Getty's fortune at $950 million this year.

Also dropping several slots was oil man and commodity trader Nelson Bunker Hunt. Last year, with a fortune worth $1.4 billion, Hunt ranked fifth on the Forbes list. This year, he dropped to 19th.

Moving into second place, up from the fourth position last year, is H. Ross Perot, founder of Electronic Data Systems and worth $1.8 billion.

Washingtonians ranked high among the nation's truly richest, with two members of the Mars family -- Forrest Edward Mars Jr. and John Franklyn Mars each listed with an $875 million share of the wealth -- making them tied for 21st place.

New to the list is Steward Bainum Sr., chairman of Manor Care Inc., with a fortune of $230 million. Also on for the first time is Bethesda construction magnate A. James Clark, who heads George Hyman Construction Co. and several affiliates, has a $165 million worth.

A total of 14 billionaires are on the mighty 400 list, including Warren E. Buffett, the Omaha businessman who in a single year parlayed his $665 million fortune into $1 billion, thanks to the more than $300 million he will make on the acquisition of General Foods Corp. by Philip Morris Inc. Buffett, also a large stockholder of two area companies -- The Washington Post Co. and Geico Corp. -- was the largest stockholder of General Foods.

Together, the average worth of the 400 is $335 million. Only 165 of the wealthiest Americans built their fortunes on their own, without significant inheritance. The Forbes list is compiled by using public disclosure documents, stock holdings and, in some cases, estimates of property and company values.

The list reflects in part the vagaries of the economy, with seven Texas oilmen dropped from the list this year. Armand Hammer, chairman of Occidental Petroleum Corp., saw his fortune drop by $50 million, to $150 million.

Owners of media property, on the other hand, saw vast improvement, making billionaires of Buffett, John Kluge and S. I. and Donald Newhouse. The 71-year-old Kluge, of Charlottesville, enriched his last year's fortune of $300 million through one of the industry's largest leveraged buyouts when he took Metromedia Inc. private. His net worth, this year, is placed at $1 billion.

Meanwhile, Rupert Murdoch made the list for the first time, with a publishing empire worth $300 million.

Katharine Graham, chairman of The Washington Post Co., saw her holdings increase from $250 million to $350 million.

The media and financial investments of Joe L. Allbritton, chairman of Riggs National Bank and owner of WJLA-TV, are worth $450 million, up $50 million from last year.

Also in the Washington area, Jack Kent Cooke, owner of the Redskins pro football team, and Paul Mellon, heir to a family fortune, remain high on the Forbes list, with each continuing to be worth $600 million.

Maryland's richest family includes Ruth Blaustein and Morton Blaustein, who control Crown Central Petroleum of Balitmore. Together their wealth is put at $675 million.

Meanwhile, Washington surgeon Laszlo Tauber has turned his real estate investing hobby into a $300 million fortune -- up $50 million from last year.

The Forbes list also includes at least two part-time Washingtonians: A. Alfred Taubman, owner of Woodward & Lothrop Inc., with $600 million -- and Mortimer Zuckerman, the owner of U.S. News & World Report, with $200 million.

The youngest member on the list is Abby Rockefeller Simpson, 28, of New York City, with an inherited $200 million fortune; the oldest is 93-year-old Dorothy Bullitt of Seattle, worth $275 million from broadcasting.