Ann Wilmer Hoon was born into a family that has run Chestertown since before the birth of George Washington. The first Wilmer died there 290 years ago. There are 11 generations of Wilmers in St. Paul's Cemetery, the Episcopal burying ground for the town's proper and powerful. Thornton, a plantation outside of town, has been in the Wilmer family for 321 years. Ann's father was the town's mayor for nearly a third of this century. He also ran the town's largest car dealership.

As soon as she could, the girl that everyone knew as "the mayor's daughter" left town.

Chestertown in the late 1940s, when she left, was a somnolent, shrinking southern town. Kent County, which surrounds the town, had 5,000 fewer residents in 1950 than at the beginning of the century. The Chesapeake Bay Bridge hadn't been completed. The town was isolated, too quiet for an ambitious young woman. Nearly every young person who could afford to, including all four of Ann's cousins, moved away.

Ann Wilmer went to Wellesley, and met and married a man from Williams College. Alexander H. (Sandy) Hoon became a steel-business executive and took his wife on a 30-year tour of Pittsburgh, Memphis, Nashville, Philadelphia and Youngstown.

Four years ago the sojourn ended, and Ann Hoon came home to the town that in the late 17th century was owned in its entirety by her ancestor Simon Wilmer. She came home with her husband to restore Thornton, the crumbling family estate, and to reassume the political influence that has been her family's birthright since white men settled Maryland's Eastern shore.

"I came back as a native," says Hoon, 55, who raised three children while she was away. "I already knew the people. It was so easy after moving in and out of places like Youngstown, Ohio, and not knowing the name of a human soul."

Hoon dresses like a corporate lawyer, in gray business suits. She keeps her blond hair cut short and wears little makeup. She describes herself as "not a society woman but a professional woman." She has no time, she says, for the elaborate dinner parties that were once a staple of Chestertown society.

She is a busy woman who, unlike most townspeople, is unavailable without an appointment. Her husband, now retired from Jones & Laughlin Steel Corporation, where he was not permitted to discuss company business with reporters, objects to his wife's answering questions about what he calls her "personal life." When she does talk about herself and her reasons for coming back home, she is cool and distant. She speaks in a clipped, precise, nonemotional way, almost as though she were describing the feelings of someone else.

Her 30 years of moving in and out of steel-town suburbs prevented her, she says, from getting involved in local politics and civic activity. After she moved home, she got involved with a vengeance.

Hoon is now co-president of the League of Women Voters, president of the United Fund and director of continuing education at Washington College. She attends county meetings and benefit cocktail parties three times a week. Last year, she ran in the Democratic primary for county commissioner.

"I would not have even considered running for office if I had not been a native," says Hoon. "People have been here for generations. They are comfortable with each other."

Hoon fell 47 votes shy of winning the primary. But she plans to run again. The other major goal of Hoon's return to Chestertown, the restoration of Thornton, has already been attained.

The 18th century brick plantation house now is an immaculate museum piece. The 700 acres of prime farm land surrounding the house are planted in corn and soybeans. The farm lands are managed by Ann Hoon's husband, who continues to work as a consultant in the steel industry.

When the Hoons came back in 1979, they found the house a shambles. It had been severely damaged by a fire in the 1920s.

They had the house stripped back to its brick frame and rebuilt. Bricks from North Carolina specially manufactured to look old were used to patch the house and build a new wing. Wood floors were rebuilt with pine stripped out of old barns in Georgia. The milk house out back was restored and converted into a pool house for the swimming pool now being dug. The Hoons have planted sugar maples along the one- half-mile driveway to the house. In their shade, the visitor is reminded of the elegance of the old South.

"Everything in this house was done by local labor," says Ann Hoon. "That is one of the reasons I like to show the house. We are proud of our local craftsmen."

While the Hoons refuse to say how much the restoration cost, they will say it was about twice as much as the cost of building a similar house from the ground up. The house and the farm have a market value of more than $400,000, according to assessment officials.

Sitting in the carefully restored, antique-furnished living room of her ancestral home, Hoon says her return to Chestertown affords her "the best of all possible worlds.

"We have a country life style, clean air and nice people. There are no traffic jams. And we are only about an hour and 45 minutes from the Kennedy Center, three hours from the theaters in New York. Most of my friends have season tickets at the Kennedy Center."

Hoon says three of her four cousins, those who left Chestertown when she did, have since returned for the same reasons that brought her back. The fourth cousin visits often.

As a budding politician and keeper of the Wilmer tradition, Hoon's major concern is making sure that Chestertown remains rural. Like most natives, she is adamantly opposed to the construction of another Bay bridge that might turn Kent County into a surburb of Baltimore.

"I want us to stay agricultural. What happened outside Washington in Montgomery and Prince George's counties, we surely don't want that here. Those places are commercial and overpopulated. That's what we in Chestertown have to be very careful about."