Following the Civil War, many Southern states administered literacy tests to prospective voters. However, some states enacted a grandfather clause in the early 1890s. The clause waived literacy tests and additional requirements for men whose descendants could vote before 1867, and African American men could not vote until 1870. Eric Foner, a Columbia University historian told NPR, "Because of the 15th Amendment, you can't pass laws saying blacks can't vote, which is what they wanted to do … But the 15th Amendment allowed restrictions that were nonracial. This was pretty prima facie a way to allow whites to vote, and not blacks." We took a 1964 Louisiana literacy test. The test was 30 questions and had to be completed in 10 minutes. One wrong answer resulted in failure.