It was necessary because after the 15th Amenment was passed (1870) some states, specially from the south, found ways to cincurmvent the amendment. So between 1870 and mid 20th century African Americans had to go through a lot of discrimination and impediments to cast their vote (such as poll taxes, white primaries, literacy tests).. . The Voting Rights of 1965 outlawed that kind of techniques (at least those that had not been declared unconstitutional then) and therefore ensured African American's right to vote. . . After the Act was passed African American vote and African American participation in the government grew a lot.