By 1842, single-member House districts had become the norm, with twenty-two states using single-member districts and only six using at-large multi-member districts. On Dec 14, 1967, single-member House districts were mandated by law (2 U.S. Code §2c), under the justification that they served as bulwarks against southern Democrats diluting the electoral power of African Americans by using strategically drawn at-large multi-member districts (they could, for instance, create a single statewide multi-member district elected by plurality vote, all but guaranteeing the white majority would elect all Democrats).