Fairfax County

Some homes in Vienna cost $1 million. Two Zip codes in Fairfax County, 22066 and 22102, had median prices of $1.2 million. (By Gerald Martineau -- The Washington Post)

The region's biggest county was also the hardest hit by last year's slowing real estate market.

In Fairfax County, home to more than 1 million people, the number of single-family houses and townhouses sold last year dropped 40 percent, compared with 2005, and the median price also fell, according to a Washington Post analysis of county sales records. Condominium sales were reviewed separately.

After years of double-digit growth, the countywide median sales price fell 1 percent, to $525,100. More than a third of Zip codes had a decline in price. The cooling market hit hardest in the middle and northern parts of the county.

In the 22031 Zip code, which includes the eastern part of Fairfax City, the median sales price fell 15 percent, to $539,950. The 20170 Zip code, Herndon, prices fell a 13 percent, to $411,000. The median price in Reston, Zip code 20190, fell 11 percent to $445,000.

Tracy Pless, an agent with Long & Foster in Reston, said the downward trend in these Zip codes stemmed from investor and speculator flight, which helped flood the market with extra inventory.

"They were buying on speculation, taking out lines of credit -- loans on their homes -- and the market turned very quickly, so the investor had to get rid of the property," she said, adding that the owners were willing to sell quickly even if that meant a loss.

Karen Trainor, managing director of the Weichert Realty's Fair Oaks office, said investors were responsible for up to a quarter of homes for sale in 2006. "Buyers had a lot more to choose from than in years past, which meant they had better bargaining power and took more time in making a decision," she said.

Not all parts of Fairfax County had price declines. In the southeastern section, which has the postal address of Alexandria, prices continued rising even though there were fewer transactions.

Prices in Belle View, Zip code 22307, rose 15 percent, to $592,000. In Hybla Valley, 22306, prices rose 6 percent, to $489,500. And in 22303, Jefferson Manor, prices were up 6 percent to $410,000.

Comparatively modest home prices, easy access to major highways and public transportation, plus great schools, make the Alexandria portion of Fairfax popular with young professionals and families alike, real estate agents said.

"People are looking for lifestyle, not just price points," said Sandra McMaster, an agent with McEnearney & Associates in Old Town.