As used by the states, the literacy test gained infamy as a means for denying suffrage to African Americans. Adopted by a number of southern states, the literacy test was applied in a patently unfair manner, as it was used to disfranchise many literate southern blacks while allowing many illiterate southern whites to vote. The literacy test, combined with other discriminatory requirements, effectively disfranchised the vast majority of African Americans in the South from the 1890s until the 1960s. Southern states abandoned the literacy test only when forced to by federal legislation in the 1960s. In 1964, the Civil Rights Act provided that literacy tests used as a qualification for voting in federal elections be administered wholly in writing and only to persons who had not completed six years of formal education. The Voting Rights Act of 1965 suspended the use of literacy tests in all states or political subdivisions in which less than 50 percent of the voting age residents were registered as of 1 November 1964, or had voted in the 1964 presidential election. In a series of cases, the Supreme Court upheld the legislation and restricted the use of literacy tests for non-English-speaking citizens. Since the passage of the civil rights legislation of the 1960s, black registration in the South has increased dramatically.