In 1914, 10-year-old Mary Kenyon watched her father and his friends build an architect-designed home on Route 123 in rural Oakton, where a trolley car ran carrying residents of the countryside to the District.

This week, 84-year-old Mary Kenyon Cross watched that same house -- her home for decades -- roll down a side street that didn't exist 70 years ago. The house, sitting on airplane tires, was being moved to a site a few blocks from the congestion of the busy Route 123 corridor. Wearing a red jacket that matched her nail polish, Mary Cross, her only daughter, Pat Price, and other family members walked arm-in-arm behind the two-story white house to its new location on one of the few empty lots remaining along Miller Road.

"I am following my house home," said Cross, who is recuperating from a recent bout with congestive heart failure.

During the last seven decades, Cross has seen the road where she rode in a horse and buggy become a major thoroughfare lined by office development. Her neighbors, young and old, have begun fighting additional commercial development until traffic problems can be solved.

"I did not mind it development . I didn't mind the noise. I enjoyed it until it squeezed me out," explained Cross, a diminutive retired insurance company employe. Over the years, the construction of Miller Road and the widening of Route 123 ate away at the 1.75 acres that once made up her homesite. She was left with only a half-acre in the middle of a dozen oak trees like those for whom an uncle of hers first named Oakton.

Several months ago, Cross got an offer from McLean-based developer Robert A. Young that she could not refuse. Young wanted her land, and in exchange for the right to purchase the valuable half-acre, he was willing to find her another lot and move the house so that she could live in it for the rest of her life.

Bo Brummett of Young & Associates said his company was looking for "commercial property in Oakton and spotted the Cross house. We wanted to turn it into a restaurant but that didn't work out," Brummett said. The size of the site would not meet county requirements for parking for a restaurant.

Young paid $65,000 for what he calls "the only lot available in the area where we could relocate the house."

In recent months, Brummett and project director Jeffrey Miricle coordinated plans to move the house with C&P Telephone, the Virginia Department of Highways and Transportation, Virginia Electric Power Co., Fairfax County officials and Media General Inc.

This week William M. Patram, a Fairfax City resident and home mover for 33 years, engineered Cross' home to its new lot. Children from Oakton Elementary School joined scores of Oakton residents for a house-moving event that might be compared with church socials held on the Cross lawn in the 1920s.

Cross will have a "life estate in the house, which will allow her to live there the rest of her life," Young explained just as Vepco cranes hoisted power lines high into the air to let the house movers slip the home onto its new lot. Cross' daughter, Price, a Prince William County employe, will live with Cross. Price agrees that Oakton has changed. She used to roller skate down Route 123 to a country store. Today that building is home to Appalachian Outfitters, one of the Northern Virginia's busiest operations catering to outdoor sports. Behind that building stands a multi-level office building facing Hunter Mill Road. Several new low-rise retail shopping centers are nearing completion.

Young plans to build a two-story office and retail building on the Cross site.

But the construction that has Oakton residents really worried is development that fills land along Route 123 near Jermantown Road near I-66. Ever since AT&T opened its giant facilities in that area, commercial development has grown at a rapid pace, county officials said. "It is hard to identify the exact boundaries of Oakton," said Ken Doggett, a Fairfax County planner specializing in the Oakton area. "The county generally looks at the headwaters of Difficult Run as the northwest boundary," Doggett said. Most people see the boundaries of Fairfax City as the southern border for Oakton.

The area's citizens association says Oakton spreads from Vienna to Fairfax City, zigzagging across the Fairfax Center area almost to Reston and back easterly to the Nutley Street area.

The Fairfax County Economic Development Authority (EDA) also has troubles defining Oakton, but, according to EDA's Steve Mields, EDA speaks of it as an arch that primarily covers the area north of I-66 in the Jermantown Road area.

Several major projects have been finished in the area recently and others are under construction. Shopping center magnate Ted Lerner, the original developer of Tysons Corner Shopping Center, has built several major buildings, Mields said. Flint Hill Centre is under construction and will provide 90,000 square feet of space. Three buildings are part of what will be known as Oakton Corporate Center. Another project by developer Damon Harwood will have 170,000 square feet.

"There is a half-million square feet of office space in the Oakton area. There will be another half-million completed by the end of 1985," Mields said. His figures do not include the AT&T building.

In recent months, Fairfax County has been asked to change its land-use plan for several sites in the area to allow commercial development or high-density residential development.

The commercial development in the Oakton area was almost certain to happen, commercial brokers said. Not only is the area convenient to I-66, but it also is squeezed between Fairfax City, the headquarters of Fairfax County's government operations and the town of Vienna. Nearby is the bustling and rapidly developing Fairfax Center area. A few miles to the north is the Tysons Corner area, which already has more office space than Richmond.

Multistory buildings in the Jermantown Road area, however disconcerting they may be to residents, have "developed essentially in conformance with the 1975 comprehensive land-use plan" for Fairfax, Doggett said.

Traffic worries Oakton residents more than development, in many cases. "The Greater Oakton Citizens Association realizes that growth is inevitable," said Linda D. Campbell, that organization's vice president.

Traffic generated by commercial development burdens Oakton's streets. Traffic barred from using I-66 during rush hours join cars from Tysons Corner to form logjams along Route 123 that spill over into residential neighborhoods. Residents and commuters complain daily about the Route 123-Hunter Mill Road intersection. Hunter Mill Road is a major, but still rural, two-lane road connecting the Oakton and Reston areas. Although intersection improvements may come in the future, Fairfax plans to maintain "the rural character of Hunter Mill Road" into the future, county officials said.

"We are fighting hard to get an overall traffic study of the entire area. We are concerned that the development of the infrastructure, like roads and sewers, are not keeping up with development. Before more development is improved, there needs to be improvements at the Route 123-Hunter Mill Road intersection," Campbell said.

Doggett said the request for such a study recently was sent from the county land-use planning office to the county Office of Transportation Planning.

"I think they [the new office buildings] are nice but they did push me straight out," Cross said.