(CNN) Here's a look at some of the most important cases decided by the US Supreme Court since 1789.
1803 - Marbury v. Madison
This decision established the system of checks and balances and the power of the Supreme Court within the federal government.
Situation: Federalist William Marbury and many others were appointed to positions by outgoing President John Adams. The appointments were not finalized before the new Secretary of State James Madison took office, and Madison chose not to honor them. Marbury and the others invoked an Act of Congress and sued to get their appointed positions.
The Court decided against Marbury 6-0.
Historical significance: Chief Justice John Marshall wrote, "An act of the legislature repugnant to the constitution is void." It was the first time the Supreme Court declared unconstitutional a law that had been passed by Congress.
1857 - Dred Scott v. Sandford
This decision established that slaves were not citizens of the United States and were not protected under the US Constitution.
Situation: Dred Scott and his wife Harriet sued for their freedom in Missouri, a slave state, after having lived with their owner, an Army surgeon, in the free Territory of Wisconsin.
The Court decided against Scott 7-2.
Historical significance: The decision overturned the Missouri Compromise, where Congress had prohibited slavery in the territories. The Dred Scott decision was overturned later with the adoption of the 13th Amendment, abolishing slavery in 1865 and the 14th Amendment in 1868, granting citizenship to all born in the United States.
1896 - Plessy v. Ferguson
This decision established the rule of segregation, separate but equal.
Situation: While attempting to test the constitutionality of the Separate Car Law in Louisiana, Homer Plessy, a man of 1/8 African descent, sat in the train car for whites instead of the blacks-only train car and was arrested.
The Court decided against Plessy 7-1.
Historical significance: Justice Henry Billings Brown wrote, "The argument also assumes that social prejudice may be overcome by legislation and that equal rights cannot be secured except by an enforced commingling of the two races... if the civil and political rights of both races be equal, one cannot be inferior to the other civilly or politically. If one race be inferior to the other socially, the Constitution of the United States cannot put them upon the same plane." The Court gave merit to the "Jim Crow" system. Plessy was overturned by the Brown v. Board of Education decision. In January 2022 Louisiana Governor John Bel Edwards granted a posthumous pardon to Homer Plessy. The pardon comes after the Louisiana Board of Pardons voted unanimously in November 2021 in favor of a pardon for Plessy, who died in his 60s in 1925.
1954 - Brown v. Board of Education
This decision overturned Plessy v. Ferguson and granted equal protection under the law.
Situation: Segregation of the public school systems in the United States was addressed when cases in Kansas, South Carolina, Delaware and Virginia were all decided together under Brown v. Board of Education. Third-grader Linda Brown was denied admission to the white school a few blocks from her home and was forced to attend the blacks-only school a mile away.
The Court decided in favor of Brown unanimously.
Historical significance: Racial segregation violates the Equal Protection Clause of the 14th Amendment.
1963 - Gideon v. Wainwright
This decision guarantees the right to counsel.
Situation: Clarence Earl Gideon was forced to defend himself when he requested a lawyer from a Florida court and was refused. He was convicted and sentenced to five years for breaking and entering.
The Court decided in favor of Gideon unanimously.
Historical significance: Ensures the Sixth Amendment's guarantee to counsel is applicable to the states through the 14th Amendment's due process clause.
1964 - New York Times v. Sullivan
This decision upheld the First Amendment rights of freedom of speech and freedom of the press.
Situation: The New York Times and four African-American ministers were sued for libel by Montgomery, Alabama, police commissioner L.B. Sullivan. Sullivan claimed a full-page ad in the Times discussing the arrest of Martin Luther King Jr., and his efforts toward voter registration and integration in Montgomery were defamatory against him. Alabama's libel law did not require Sullivan to prove harm since the ad did contain factual errors. He was awarded $500,000.
The Court decided against Sullivan unanimously.
Historical significance: The First Amendment protects free speech and publication of all statements about public officials made without actual malice.
1966 - Miranda v. Arizona
The decision established the rights of suspects against self-incrimination.
Situation: Ernesto Miranda was convicted of rape and kidnapping after he confessed, while in police custody, without benefit of counsel or knowledge of his constitutional right to remain silent.
The court decided in favor of Miranda 5-4.
Historical significance: Upon arrest and/or questioning, all suspects are given some form of their constitutional rights - "You have the right to remain silent. Anything you say can and will be used against you in a court of law. You have the right to an attorney. If you cannot afford an attorney, one will be provided for you. Do you understand the rights I have just read to you? With these rights in mind, do you wish to speak to me?"
1973 - Roe v. Wade
This decision expanded privacy rights to include a woman's right to choose pregnancy or abortion.
Situation: "Jane Roe" (Norma McCorvey), single and living in Texas, did not want to continue her third pregnancy. Under Texas law, she could not legally obtain an abortion.
The Court decided in favor of Roe 7-2.
Historical significance: Abortion is legal in all 50 states. Women have the right to choose between pregnancy and abortion.
1974 - United States v. Nixon
This decision established that executive privilege is neither absolute nor unqualified.
Situation: President Richard Nixon's taped conversations from 1971 onward were the object of subpoenas by both the special prosecutor and those under indictment in the Watergate scandal. The president claimed immunity from subpoena under executive privilege.
The Court decided against Nixon 8-0.
Historical significance: The president is not above the law. After the Court ruled on July 24, 1974, Richard Nixon resigned on August 8.
1978 - Regents of the U. of California v. Bakke
This decision ruled that race cannot be the only factor in college admissions.
Situation: Allan Bakke had twice applied for and was denied admission to the University of California Medical School at Davis. Bakke was white, male and 35 years old. He claimed under California's affirmative action plan, minorities with lower grades and test scores were admitted to the medical school when he was not, therefore his denial of admission was based solely on race.
The Court decided in Bakke's favor, 5-4.
Historical significance: Affirmative action is approved by the Court and schools may use race as an admissions factor. However, the Equal Protection Clause of the 14th Amendment works both ways in the case of affirmative action; race cannot be the only factor in the admissions process.
Situation: The constitutionality of the sweeping health care reform law championed by President Barack Obama.
The Court voted 5-4 in favor of upholding the Affordable Care Act.
Historical significance: The ruling upholds the law's central provision - a requirement that all people have health insurance or pay a penalty.
2013 - United States v. Windsor
This decision ruled that the Defense of Marriage Act, which defined the term "marriage" under federal law as a "legal union between one man and one woman" deprived same-sex couples who are legally married under state laws of their Fifth Amendment rights to equal protection under federal law.
Situation: Edith Windsor and Thea Spyer were married in Toronto in 2007. Their marriage was recognized by New York state, where they lived. Upon Spyer's death in 2009, Windsor was forced to pay $363,000 in estate taxes, because their marriage was not recognized by federal law.
The court voted 5-4 in favor of Windsor.
Historical significance: The court strikes down section 3 of the Defense of Marriage Act, ruling that legally married same-sex couples are entitled to federal benefits.
2015 - King et al, v. Burwell, Secretary of Health and Human Services, et al
Situation: This case was about determining whether or not the portion of the Affordable Care Act which says subsidies would be available only to those who purchase insurance on exchanges "established by the state" referred to the individual states.
The Court ruled 6-3 in favor of upholding the Affordable Care Act subsidies.
Historical significance: The court rules that the Affordable Care Act federal tax credits for eligible Americans are available in all 50 states, regardless of whether the states have their own health care exchanges.
2015 - Obergefell et al, v. Hodges, Director, Ohio Department of Health, et al.
Situation: Multiple lower courts had struck down state same-sex marriage bans. There were 37 states allowing gay marriage before the issue went to the Supreme Court.
The Court ruled 5-4 in favor of Obergefell et al.
Historical significance: The court rules that states cannot ban same-sex marriage and must recognize lawful marriages performed out of state.
2016 - Fisher v. University of Texas
Situation: Abigail Fisher sued the University of Texas after her admission application was rejected in 2008. She claimed it was because she is white and that she was being treated differently than some less-qualified minority students who were accepted. In 2013 the Supreme Court sent the case back to the lower courts for further review.
The Court ruled 4-3 in favor of the University of Texas. Justice Elena Kagan recused herself from the case, presumably because she dealt with it in her previous job as solicitor general.
Historical Significance: The court rules that taking race into consideration as one factor of admission is constitutional.
2020 - Bostock v. Clayton County, Georgia
Situation: Gerald Bostock filed a lawsuit against Clayton County for discrimination based on his sexual orientation after he was terminated for "conduct unbecoming of its employees," shortly after he began participating in a gay softball league. Two other consolidated cases were also argued on the same day.
The 6-3 opinion in favor of the plaintiff, written by Justice Neil Gorsuch and joined by Chief Justice John Roberts, states that being fired "merely for being gay or transgender violates Title VII" of the Civil Rights Act of 1964.
Historical Significance: Federal anti-bias law now protects people who face job loss and/or discrimination based on their sexual orientation or gender identity.
2022 - Dobbs v. Jackson Women's Health Organization
Situation: Mississippi's Gestational Age Act, passed in 2018 and which greatly restricts abortion after 15 weeks, is blocked by two federal courts, holding that it is in direct violation of Supreme Court precedent legalizing abortion nationwide prior to viability, which can occur at around 23-24 weeks of pregnancy, and that in an "unbroken line dating to Roe v. Wade, the Supreme Court's abortion cases have established (and affirmed and re-affirmed) a woman's right to choose an abortion before viability." The court said states may "regulate abortion procedures prior to viability" so long as they do not ban abortion. "The law at issue is a ban," the court held.
Mississippi appeals the decision to the Supreme Court.
The 6-3 opinion in favor of the plaintiff, written by Justice Samuel Alito states that "Roe was egregiously wrong from the start...Its reasoning was exceptionally weak, and the decision has had damaging consequences. And far from bringing about a national settlement of the abortion issue, Roe and Casey have enflamed debate and deepened division."
In a joint dissenting opinion, Justices Stephen Breyer, Sonia Sotomayor and Elena Kagan heavily criticized the majority, closing: "With sorrow -- for this Court, but more, for the many millions of American women who have today lost a fundamental constitutional protection -- we dissent."
Historical Significance: The ruling overturns Roe v. Wade and there is no longer a federal constitutional right to an abortion, leaving abortion rights to be determined by states.
1944 - Korematsu v. United States - The Court ruled Executive Order 9066, internment of Japanese citizens during World War II, is legal, 6-3 for the United States.
1961 - Mapp v. Ohio - "Fruit of the poisonous tree," evidence obtained through an illegal search, cannot be used at trial, 6-3 for Mapp.
1967 - Loving v. Virginia - Prohibition against interracial marriage was ruled unconstitutional, 9-0 for Loving.
1968 - Terry v. Ohio - Stop and frisk, under certain circumstances, does not violate the Constitution. The Court upholds Terry's conviction and rules 8-1 that it is not unconstitutional for police to stop and frisk individuals without probable cause for an arrest if they have a reasonable suspicion that a crime has or is about to occur.
2008 - District of Columbia v. Heller - The Second Amendment does protect the individual's right to bear arms, 5-4 for Heller.
2010 - Citizens United v. FEC - The Court rules corporations can contribute to PACs under the First Amendment's right to free speech, 5-4 for Citizens United.
2023 - Students for Fair Admissions v. Harvard together with Students for Fair Admissions v. University of North Carolina - Colleges and universities can no longer take race into consideration as a specific basis in admissions. The majority opinion, written by Justice John Roberts, claims the court is not expressly overturning prior cases authorizing race-based affirmative action and suggests that how race has affected an applicant's life can still be part of how their application is considered.
2024 - Donald J. Trump v. Norma Anderson, et al - The Court rules former President Donald Trump should appear on the ballot in Colorado in a decision that follows months of debate over whether Trump violated the "insurrectionist clause" included in the 14th Amendment.