The Home Owners' Loan Corporation was established in 1933 by the U.S Congress to refinance mortgages in default and prevent foreclosures. In 1935 they created residential security maps for 239 cities to indicate the level of security for real-estate investments. The maps were graded such as the newest areas, which were considered desirable for lending received a "Type A" grade. These areas were primarily wealthy suburbs on the outskirts of town. Still Desirable neighborhoods were given a "Type B" grade and older neighborhoods were given a "Type C" grade and considered Declining. Lastly "Type D" neighborhoods were regarded as most risky for mortgage lending.Wikipedia - http://en.wikipedia.org/wiki/Redlining