Take a gander of this map of Milwaukee's segregation maps from the 2000 and 2010 U.S. Census Bureau.
Did you know that the Greater Milwaukee/Waukesha Metro Area is the #1 most segregated place in the United States? Why do you suppose it's still this way?
Each Blue Dot = 200 African American Residents
Each Orange Dot = 200 White Residents
Source: "Residential Segregation of Blacks or African Americans: 1980-2000." US Census Bureau
http://www.census.gov/hhes/www/housing/housing_patterns/pdf/ch5.pdf
Here's a Segregation map for the 2010 Census, too,
which brings in more than just black and white residents:
Source: Sharp, Gwen. The Society Pages. "2010 Census Data on Residential Segregation."
http://thesocietypages.org/socimages/2011/03/30/2010-census-data-on-residential-segregation/