After Reconstruction ended, African Americans' right to vote, given in the 15th Amendment, was abridged in the South. Local voting commissions imposed laws that restricted their right to vote. These restrictions included grandfather clauses that prohibited people from voting if their grandfathers had not voted. As African Americans' ancestors had been enslaved, grandfather clauses restricted their right to vote. In addition, literacy tests, often made harder for blacks than whites, restricted black people's rights to vote, as did poll taxes, in which people had to pay to vote. Whites also used intimidation and violence to restrict the right to vote. Black people who insisted on registering to vote were often met with the threat of violence or actual violence though organizations such as the Ku Klux Klan and later through White Citizens' Councils. They were also often not allowed to work if they tried to register to vote.