
Those counties, spread over a dozen states, accounted for more than 1.5 million foreclosure actions last year, a USA TODAY analysis of figures compiled by the real estate listing firm RealtyTrac shows — more than were recorded in the entire United States just two years earlier. They were the epicenter of a wave of foreclosures that have left leading banks teetering and magnified the nation's economic problems.
"This crisis was triggered by foreclosures, and a lot of those were in a very small number of areas," says William Lucy, a University of Virginia professor who has studied the link between lenders and faltering home loans. Banks spread the risk and "it became like a car with no reverse gear. Once it starts to go over the cliff, it's gone."

A few of the 35 counties leading the foreclosure boom are in already-distressed areas around Detroit and Cleveland. But most are clustered in places such as Southern California, Las Vegas, Phoenix, South Florida and Washington, where home values shot up dramatically in the first half of the decade, then began to crumble.