This year, for the first time, Local Leaders includes markets 51 through 75. As the top 50 markets have grown crowded, national builders bent on expansion have reached down to this second tier, which produces roughly 5,000 homes or more per market. Builders' thinking: If they can secure a 20 percent share, that translates into 1,000 homes, enough to sustain a division.

But few locations appear ripe for easy picking. A close inspection of second-tier markets shows that many are already full of competition. For instance, the top 10 builders build 43.0 percent of the homes in Fresno, Calif., No. 51 on our list. In Oakland, Calif., the 53rd-largest market, the top 10 control an astounding 92.2 percent of the market. And in Fort Lauderdale, Fla., ranked 72nd, the top 10 build nearly half the homes in the market.

By the same token, some of the top 50 markets literally have been overtaken by the biggest builders, leaving little more than table scraps for others. In Sacramento, Calif. (No. 13), for example, the 10 biggest build six out of every 10 homes. In Denver (No. 16), it's even worse—the top 10 command almost 70 percent of the market.

Some markets are overrun with public builders intent on fueling a voracious appetite for growth. Consider that only two private builders appear on the top 10 list in Las Vegas and Washington, where the top 10 national builders command 84 percent and 69.5 percent shares of the markets, respectively.

At the other extreme, none of the top 10 national builders builds in four of our new markets, Louisville, Ky.; New Orleans; Omaha, Neb.; and Mobile, Ala. And only one national shows up among the top 10 in St. Louis, where all it takes is 85 closings to make the list. Of course, you may need a close relative in the land development business to enter that market.

Other markets continue to befuddle big builders. In Atlanta, now the second-largest metro market, the top builder, Pulte, did only 1,585 homes, for a 2.8 percent market share. Testament to the difficulty of doing business there, Morrison Homes recently closed down its Atlanta operation. It couldn't achieve enough scale because the region is carved up into so many political jurisdictions and there are so many small and nimble competing builders.

And then there is Kansas City (Mo./Kan.), perennially the market most difficult for any one builder to dominate. The biggest builders there, Pulte Homes and Rob Washam Homes, each closed only 205 homes in 2004—a 1.7 percent market share for each company. Kansas City produced 12,347 single-family permits in 2004, more than San Antonio, where the top 10 builders own a staggering 65.9 percent of the market.

Learn more about markets featured in this article: Kansas City, MO.