Communities across the country that didn't participate in the housing boom have also missed out on the mortgage crisis, reports Forbes. Those areas now comprise the strongest housing markets in the nation, and Pittsburgh is among them.

It's a similar story for the old industrial town of Pittsburgh, Pa. The city built on steel had its crisis two decades ago. Now, it's one of America's cleanest cities. Carnegie Mellon University attracts some of the best and brightest students, and some of the old steel mills are being converted to research parks. Pittsburgh is grayer than most cities: 16% of the population is over 65, well above the national average of 12%. Retirees, living on social security and pensions, are less affected by job losses.

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