why did African Americans in the South lose many of their civil rights until 1950s and 1960s?

please help me

These may help you --

http://memory.loc.gov/learn/features/civilrights/flash.html

and others:
http://www.google.com/search?q=history+civil+rights&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7SUNA