The answer in this question is The Voting Rights Act of 1965. In the year 2006 congress expanded the voting rights act of 1965 for another 25 years, responding to charges that black voters still faces discrimination at the polls. The voting rights act of 1965 is signed by president President Lyndon Johnson (1908-73) on August 6, 1965, and it is the landmark piece of federal legislation in the US that prohibits racial discrimination in voting.
