Grandfather clauses were provisions set up by several Southern states after Reconstruction which allowed potential white voters who failed literacy tests or could not afford poll taxes to still be eligible for voting if their grandfathers had been eligible to vote.
15th Amendment : An amendment added to the U.S Constitution that prohibits the federal and state governments from denying a citizen the right to vote based on that citizen's "race, color, or previous condition of servitude".
Reconstruction Era : The period after the Civil War in which attempts were made to redress the inequities of slavery and its political, social, and economic legacy.
Plessy v. Ferguson : A landmark 1896 U.S. Supreme Court decision that upheld racial segregation under the doctrine of "separate but equal".