Dred Scott v. Sandford, 60 U.S. (19 How.) 393 (1857), was a landmark decision of the United States Supreme Court in which the Court held that the United States Constitution was not meant to include American citizenship for people of African descent, regardless of whether they were enslaved or free, and so the rights and privileges that the Constitution confers upon American citizens could not apply to them. The Supreme Court's decision has been widely denounced, both for how overtly racist the decision was and its crucial role in the start of the American Civil War four years later. Legal scholar Bernard Schwartz said that it "stands first in any list of the worst Supreme Court decisions". Chief Justice Charles Evans Hughes called it the Court's "greatest self-inflicted wound". Historian Junius P. Rodriguez said that it is "universally condemned as the U.S. Supreme Court's worst decision." Historian David Thomas Konig said that it was "unquestionably, our court's worst decision ever."The decision was made in the case of Dred Scott, an enslaved black man whose owners had taken him from Missouri, a slave-holding state, into Illinois and the Wisconsin Territory, where slavery was illegal. When his owners later brought him back to Missouri, Scott sued in court for his freedom and claimed that because he had been taken into "free" U.S. territory, he had automatically been freed and was legally no longer a slave. Scott sued first in Missouri state court, which ruled that he was still a slave under its law. He then sued in U.S. federal court, which ruled against him by deciding that it had to apply Missouri law to the case. He then appealed to the U.S. Supreme Court.

In March 1857, the Supreme Court issued a 72 decision against Scott. In an opinion written by Chief Justice Roger Taney, the Court ruled that people of African descent "are not included, and were not intended to be included, under the word 'citizens' in the Constitution, and can therefore claim none of the rights and privileges which that instrument provides for and secures to citizens of the United States". Taney supported his ruling with an extended survey of American state and local laws from the time of the Constitution's drafting in 1787 that purported to show that a "perpetual and impassable barrier was intended to be erected between the white race and the one which they had reduced to slavery". Because the Court ruled that Scott was not an American citizen, he was also not a citizen of any state and, accordingly, could never establish the "diversity of citizenship" that Article III of the U.S. Constitution requires for a U.S. federal court to be able to exercise jurisdiction over a case. After ruling on those issues surrounding Scott, Taney continued further and struck down the entire Missouri Compromise as a limitation on slavery that exceeded the U.S. Congress's constitutional powers.

Although Taney and several other justices hoped the decision would permanently settle the slavery controversy, which was increasingly dividing the American public, the decision's effect was the opposite. Taney's majority opinion suited the slaveholding states, but was intensely decried in all the other states. The decision inflamed the national debate over slavery and deepened the divide that led ultimately to the American Civil War. In 1865, after the Union's victory, the Court's ruling in Dred Scott was superseded by the passage of the Thirteenth Amendment to the U.S. Constitution, which abolished slavery, and the Fourteenth Amendment, whose first section guaranteed citizenship for "all persons born or naturalized in the United States, and subject to the jurisdiction thereof".

The United States Congress is the legislature of the federal government of the United States. It is bicameral, being composed of a lower body, the House of Representatives, and an upper body, the Senate. The Congress meets in the United States Capitol in Washington, D.C. Both senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a governor's appointment. Congress has 535 voting members: 100 senators and 435 representatives. The vice president of the United States has a vote in the Senate only when senators are evenly divided. The House of Representatives has six non-voting members.The sitting of a Congress is for a two-year term, at present, beginning every other January. Elections are held every even-numbered year on Election Day. The members of the House of Representatives are elected for the two-year term of a Congress. The Reapportionment Act of 1929 establishes that they be elected in single-member constituencies or districts by first-past-the-post and that Congressional districts be apportioned to states by population every ten years using the United States Census results, provided that each state has at least one Congressional representative. Each senator is elected at-large in their state for a six-year term, with terms staggered, so every two years approximately one-third of the Senate is up for election. Each state, regardless of population or size, has two senators, so currently, there are 100 senators for the 50 states.

Article One of the United States Constitution requires that members of Congress must be at least 25 years old (House) or at least 30 years old (Senate), have been a citizen of the United States for seven (House) or nine (Senate) years, and be an inhabitant of the state which they represent. Members in both chambers may stand for re-election an unlimited number of times.

The Congress was created by the Constitution of the United States and first met in 1789, replacing in its legislative function the Congress of the Confederation. Although not legally mandated, in practice since the 19th century, Congress members are typically affiliated with one of the two major parties, the Democratic Party or the Republican Party, and only rarely with a third party or independents affiliated with no party. In the case of the latter, the lack of affiliation with a political party does not mean that such members are unable to caucus with members of the political parties. Members can also switch parties at any time, although this is quite uncommon.