Joseph Johnson, 63, was born in a white frame house that sits on the 380 acres he farms in Manassas. His parents Wheatley and Dorothy Johnson were farmers there, too. They are buried in a small family cemetery not far from Joseph's home, resting in the land they worked and loved.

But soon, 200 years of Johnson farming at Clover Hill will end. Joseph, his brother Bill and their aunt Alice have yielded to a foe that neither pesticides nor irrigation could defeat: urbanization.

The Johnsons have an agreement to sell their dairy farm to the development firm of Kettler & Scott pending city approval. Within a year, the herd of 150 Jersey cows and rolling pastures will give way to a $300 million residential and commercial project proposed by the Northern Virginia developers.

"The thing that scares all of us is a loss of a sense of freedom," said Joseph Johnson, who lives in one of three houses on the property. "I don't really know where I am going. I'm not sure I'll like living in a subdivision. I'm not sure I'll like the loss of privacy. It's kind of a helpless feeling. The only thing you can do is move . . . . But that's what they call progress."

Alice Johnson, the 74-year-old family historian, said the Johnsons knew the change would come eventually, but it was still a shock when the decision was finally made.

The Johnsons say they are willing to sell their land because operating a dairy farm is no longer economical and because it was becoming increasingly difficult to work a farm in one of Virginia's fastest growing cities.

Joseph Johnson declined to disclose the terms of the deal, but city officials said property in the area near the farm has sold for $45,000 an acre and more. Johnson said he considered the developers' offer good, yet family members indicated that a price tag cannot be placed on heritage.

"It was a heartbreaking and emotional decision," Alice Johnson said. "Every tree has a history, every plant . . . . I am leaving. The emotional strain of seeing things torn down would be a little hard to take." She said she will be moving to Blacksburg, Va.

In 1854, Alice's great-grandmother Eliza Wheatley Johnson was left pregnant with four children to rear after her husband died, Alice said. Eliza managed to keep the farm going, but during the Civil War, when the farmhouse was burned by Union soldiers, she moved to a plantation in Appomattox. At the war's end, returned to Clover Hill to rebuild the farmhouse, Alice said.

"Eliza could fight what the war brought and survive, but we can't fight urbanization," she said.

Subdivisions border every side of the farm except one. When Joseph and Bill get up between 4 and 6 a.m., they are greeted by commuters driving along Clover Hill Road, which separates the grazing area from the barn. A few weeks ago, Bill had to get up in the middle of the night to mend a fence smashed by a car.

The Johnsons reached a decision made by other farmers in the county and across the country. From 1982 to 1986, more than 10,000 acres of county land was rezoned from agricultural to other uses. Nationwide, more than 148,000 farms ceased operation between 1980 and 1985, according to government statistics.

Joseph Johnson, wearing black framed glasses, a flannel shirt and the leathery wrinkles he has earned from years in the sun, can remember much simpler days.

They were days spent hunting, fishing and harvesting corn, wheat, peanuts and garden vegetables, when neighbors would take turns helping one another bring in the crops. "You ate wherever you went," Johnson laughed. "There was a little competition amongst the farmers' wives as to who could set the best table."

Farming was not just a job, Johnson said. "You have a love for the land. You develop a respect for nature . . . . It's a challenge. You've got to get the crops in before the storm."

Even in rearing children, farming was important, he said. "I don't think there is any better place to raise a child than on a farm. If you give a child an animal to take care of, it teaches responsibility."

Bill Johnson's son Keith, 25, is the sixth generation of Johnsons to farm the land since Rut Johnson bought the first parcel of 30 acres for 50 pounds on Sept. 7, 1770.

"Memories. There are just so many," Keith said. "My fondest memory would be the day my grandfather gave me my first calf for my 4-H project." He was 9 years old and the calf's name was Triumph Iris. "Responsibility. It was my first step toward that."

Keith juggles his job as a part-time clerk in a drug store with farming with his brother Richard, 23. "I look at it as a job. Parts of it are fun and parts are not. It does give you a good feeling of accomplishment, like you have done something right."

Richard said he doesn't expect to continue farming after the farm is sold, although he is not sure what he will do. Keith plans to become a police officer.

As dusk approached one day last week, Joseph walked into the barn to see Keith and Richard at work, methodically attaching the milking machines to a platoon of brown cows. Joseph stood for a second, watching as milk flowed from the milking machines into pipes that would carry it to a tank in an adjacent building.

"There comes a time," Joseph said recently, "when crops mature and land develops."