For African Americans, the passage of the Voting Rights Act on Aug. 6, 1965, represented the culmination of a centuries-long struggle for citizenship. President Lyndon Johnson’s signing of the legislation, designed to end a century of voter disfranchisement in the South and other parts of the nation, was inspired by grassroots protests and organizing that gripped the nation. Martin Luther King Jr.’s efforts in Selma, Ala., linked a local campaign for voting rights to a national movement to redefine American democracy.