From the U.S. Census:
The fact sheets released today provide information on 25 selected metropolitan areas’ housing costs, mortgages and a variety of other physical and financial characteristics. A national fact sheet is also available.
The statistics come from the American Housing Survey, which is sponsored by the Department of Housing and Urban Development (HUD) and conducted by the U.S. Census Bureau, and is the most comprehensive housing survey in the United States. National data are collected every odd-numbered year and metropolitan area data are collected on a rotating basis.
All fact sheets are available in PDF.