The Civil War ended in April 1865, the same month that President Lincoln was assassinated. The Republican Party dominated Congress and set about to “reconstruct” the South legally, economically, and politically. Some of its measures appeared to have the goal of punishing the states that had seceded from the union. Others were aimed at protecting former slaves, including three constitutional amendments:
Thirteenth Amendment (1865): Prohibits slavery or involuntary servitude, except as punishment for a crime for which a person has been convicted.
Fourteenth Amendment (1868): Defines citizenship based on birth in the United States and state residency; prohibits states from making or enforcing laws abridging the privileges or immunities of citizens of the United States; prohibits states from denying any person life, liberty or property without due process of law; prohibits states from denying any person in their jurisdiction equal protection of the laws.
Authorizes reduction in congressional representation for states depriving any male having attained age 21 the right to vote.
Prohibits federal and state office holding by anyone engaged in rebellion against the United States, and gives Congress power to make exceptions by extraordinary majority vote.
Holds states that rebel against the Union liable for their debts.
Fifteenth Amendment (1870): Prohibits states from denying the right to vote on account of race, color, or previous condition of servitude.
Each of those amendments gave Congress a broad new power: to enforce the amendment “by appropriate legislation.” This grant of power to Congress increased the powers of the federal courts as well, both through the power to construe the meaning of statutes passed under the authority of the amendments and the power to determine whether those statutes are constitutional.