Supreme Court Strikes Down Grandfather Clauses in Guinn v. United States

In Guinn v. United States, the Supreme Court unanimously struck down Oklahoma's grandfather clause, which exempted men whose ancestors could vote before 1866 from literacy tests, effectively protecting illiterate white voters while subjecting all Black voters to the tests. It was the NAACP's first major Supreme Court victory and the first time the Court struck down a law as a violation of the 15th Amendment since Reconstruction.