In Berman v. Parker (348 U.S. 26 (1954)), DC was trying to rehabilitate a "blighted" area of the city.  Most of the homes were completely beyond repair and abandoned.  However, there was a department store in the rehabilitation zone that claimed it was not "blighted."  The US Supreme Court found that eminent domain should be decided "as a whole", and not in a piecemeal fashion.

• Basically, this case established that the government can use eminent domain to rehabilitate a "blighted" area, even if they intend to simply give the land to a private developer, and even if not every single building within the area is "blighted."
• Compare this to the later case of Kelo v. City of New London (125 S. Ct. 2655 (2005)).  There, the US Supreme Court expanded the power of eminent domain to allow the government to use eminent domain to rehabilitate an area that isn't blighted at all.
• In Berman v. Parker, the city was attempting to build low-income housing that would theoretically be enjoyed by the same people who were being kicked out.  In Kelo v. City of New London, the city was going to build an industrial park, which would not directly benefit the people who were being kicked out.