Constitution of the United States
Safeguards of civil rights (Amendments 13, 14, 15, 19, 23, 24, and 26)

The Thirteenth Amendment (1865) abolished slavery and involuntary servitude, except as punishment for a crime, and authorized Congress to enforce abolition. Though millions of slaves had been declared free by the 1863 Emancipation Proclamation, their post Civil War status was unclear, as was the status of other millions. Congress intended the Thirteenth Amendment to be a proclamation of freedom for all slaves throughout the nation and to take the question of emancipation away from politics. This amendment rendered inoperative or moot several of the original parts of the constitution.

The Fourteenth Amendment (1868) granted United States citizenship to former slaves and to all persons "subject to U.S. jurisdiction." It also contained three new limits on state power: a state shall not violate a citizen's privileges or immunities; shall not deprive any person of life, liberty, or property without due process of law; and must guarantee all persons equal protection of the laws. These limitations dramatically expanded the protections of the Constitution. This amendment, according to the Supreme Court's Doctrine of Incorporation, makes most provisions of the Bill of Rights applicable to state and local governments as well. It superseded the mode of apportionment of representatives delineated in Article 1, Section 2, Clause 3, and also overturned the Supreme Court's decision in Dred Scott v. Sandford (1857).

The Fifteenth Amendment (1870) prohibits the use of race, color, or previous condition of servitude in determining which citizens may vote. The last of three post Civil War Reconstruction Amendments, it sought to abolish one of the key vestiges of slavery and to advance the civil rights and liberties of former slaves.

The Nineteenth Amendment (1920) prohibits the government from denying women the right to vote on the same terms as men. Prior to the amendment's adoption, only a few states permitted women to vote and to hold office.

The Twenty-third Amendment (1961) extends the right to vote in presidential elections to citizens residing in the District of Columbia by granting the District electors in the Electoral College, as if it were a state. When first established as the nation's capital in 1800, the District of Columbia's five thousand residents had neither a local government, nor the right to vote in federal elections. By 1960 the population of the District had grown to over 760,000.

The Twenty-fourth Amendment (1964) prohibits a poll tax for voting. Although passage of the Thirteenth, Fourteenth, and Fifteenth Amendments helped remove many of the discriminatory laws left over from slavery, they did not eliminate all forms of discrimination. Along with literacy tests and durational residency requirements, poll taxes were used to keep low-income (primarily African American) citizens from participating in elections. The Supreme Court has since struck down these discriminatory measures.

The Twenty-sixth Amendment (1971) prohibits the government from denying the right of United States citizens, eighteen years of age or older, to vote on account of age. The drive to lower the voting age was driven in large part by the broader student activism movement protesting the Vietnam War. It gained strength following the Supreme Court's decision in Oregon v. Mitchell (1970).
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