The Black Codes and Jim Crow laws that brought racial segregation to many parts of the U.S. were a result of the enslavement of African-Americans. Remember -- that until 1865, many whites believed that it was only right that blacks were inferior and should be slaves. Since people don't change their minds over night -- or even in a generation or two, some whites continued the practice segregation to separate themselves from the former slaves and their descendants. Check these sites for more information.
http://www.spartacus.schoolnet.co.uk/USAjimcrow.htm
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http://en.wikipedia.org/wiki/Racial_segregation#United_States_.2819th-21st_century.29
If segregation was really bad ,why did it start in the first place?
2 answers
My opinion - descendents of the "British Empire" have long had an over inflated opinion of their importance and worth. I might also point out that they held the "natives" of every one of their "conquered" nations in disregard whether it be India, Africa , Ireland or the New World. In addition , Writeacher has pointed out that "segregation" has taken place in many different societies over the ages; ie. the caste system in India. The attitude of "we are better" is easy to propogate..... far easier than "doing better".