The last great expanse of developable property near Gaithersburg is the Crown Farm, with its rolling hills and freshly cut grass, nestled near Interstate 270 and the heart of Montgomery County's biotech community. It is such an irresistible jewel for home builders that bidding for the property at times resembled begging.

So when Los Angeles-based KB Home swooped in on the 180-acre property this summer as lead builder in a $137 million, 2,000-house deal, the region's home builders did not need to be told the ground underneath them had shifted. The nation's fifth-largest builder, with $7 billion in revenue last year, jolted the country's fastest-growing home-building market, setting the stage for even sharper battles between regional and national builders for a limited amount of land.

"We are all absolutely fierce competitors," said G. Cory DeSpain, who oversees home building in Virginia and Maryland for Pennsylvania-based Toll Brothers Inc., which deals mainly in luxury homes. "They will find their market niche here. They have deep pockets. They are a big company. They're probably going to take some market share from people."

The question is: From whom? As in other urban locations, the region's home-building market is dominated by more than a dozen national builders. The competition is fractured, though, with no single builder getting more than 10 percent of home sales. The perennial leader is Reston-based NVR Inc., which operates under five brands, including Ryan Homes. NVR led the region in 2004 with 2,477 sales -- an 8.2 percent market share -- making it the most likely market-share loser because of increased competition spurred by KB Home.

KB's entrance into the market is also likely to affect regional builders such as the Stanley Martin Cos., Craftmark Homes Inc., Miller & Smith Inc., Bozzuto Homes Inc., and others that increasingly compete with the larger companies on smaller projects.

After courting the Crown family for a decade, Aris Mardirossian, a local businessman, fielded sale and partnership offers from home builders around the region, the country and the world. He did so remembering a promise he made to the family -- to bring in a company that would not build a standard Main Street community. Nothing raised his eyebrows.

So he and his partner, Steve Lebling, essentially gave up. They decided to forgo a big builder, finance the purchase themselves and sell off parts of the property to individual home builders. Then KB Home came calling. The builder had just moved into the Washington region. It was looking for a signature deal.

"A lot of the big guys looked at this project said, 'I have this type of house sitting on my shelf and I'll just pull it off the shelf and slap it in,' " said Steve Coniglio, KB's local vice president for land acquisition. "We said we would look at it with fresh eyes."

Besides coming up with more than $100 million -- the project also has financial backing from Centex Homes -- KB offered a vision for a new urbanist community, relying heavily on mass transit: think downtown, Connecticut Avenue in the suburbs, with modern cityscape architecture, maybe even stacked townhouses. The negotiations lasted a couple of hours.

"We both wanted to create a jewel for Gaithersburg," Mardirossian said.

Only 10 years ago, KB Home was heavily focused on its back yard in California, building about 8,000 houses a year, mostly starter homes. But led by Chairman Bruce E. Karatz -- who built, in Las Vegas, a replica neighborhood of "The Simpsons" family house and just formed a partnership with Martha Stewart -- KB moved east, selling bigger, more expensive homes to up-and-coming professionals. KB now ranks first in home sales in Tucson; second in Jacksonville, Fla., and San Antonio; and third in Denver. It built 31,646 homes last year.

"They are taking market share from other builders wherever they go," said James F. Wilson, an analyst with JMP Securities LLC. "They consider markets interesting to enter if they can do a couple thousand houses a year."

Because of the tight land supply, KB is approaching the Washington market in the way other national builders have recently: going after big, signature projects while also fighting for smaller deals against regional home builders such as Stanley Martin, Craftmark, Miller & Smith, and Bozzuto.

Besides Crown Farm, KB is planning 304 houses on 850 rural acres in Loudoun County. It is building a couple of dozen houses in Prince George's County, and it recently made a deal for 32 townhouse lots in Gaithersburg. Other projects are in the works.

"I think people perceive us national builders as only being interested in the big deals," DeSpain said. "That's not the case. We want to do the big deals. We also want to do the small deals."

That has made doing business more difficult for the regional home builders, which often focus on small or medium-size deals. How KB will affect the situation is unclear.

"When I look at KB Home, right now I have competition from 15 national home builders, so KB will make it 16, and that's really not too big a deal given I'm already competing against them anyway," said Steven B. Alloy, president of Stanley Martin.

Regional builders have also always had a distinct disadvantage against the nationals in that their pockets are not as deep. The inability to write big checks for property has become more of a problem as the national builders increasingly go after smaller projects, willing at times to overpay for them.

Alloy and other regional home builders recently devised a solution to that problem: raising money through the public financial markets. Stanley Martin recently issued $125 million worth of junk bonds.

"There is no situation now where we are at a disadvantage," Alloy said. "We didn't want [the national builders] to have a capital advantage over us."

Regional builders do have one advantage over national builders: their long-standing relationships with local government officials, who can help guide projects through the approval process, sometimes with better results. In many residential land deals, prices are set by how many lots a builder can get approved.

"In our market, the ability to get government approval is a big deal, and newcomers will always have a hard time with that," Alloy said.

Senior executives at KB Home think they solved that problem by hiring Coniglio to run its day-to-day operations in the region.

Coniglio has worked locally in the industry for 17 years, including most recently for national builder Pulte Homes Inc. He hired about 15 people, many with local connections. He bought the land in Loudoun County from Centex Homes and the land in Prince George's County from several developers. Both already had partial approvals from government officials. With the Crown Farm development, KB Home decided to pursue having the land annexed into Gaithersburg from Montgomery County, thereby avoiding a lengthy and complicated, and recently controversial, development review process.

"When we are done here," Coniglio said, "I want to see a wall of awards. That's our goal."

KB Home's Steve Coniglio on the site of a planned $137 million development near Gaithersburg. KB is to be the lead builder on the 2,000-home project, to be built on the former Crown Farm.KB Home built a house modeled on the cartoon home of "The Simpsons." KB Home Chairman Bruce E. Karatz, right rear, appeared with the crew of "Extreme Makeover: Home Edition" and a family for which KB built a house.Martha Stewart Living Omnimedia and KB Home said they would work together to build a new line of houses. The first project, in Cary, N.C., will include the Lily Pond model, above.