A summary of the US Constitution starts with what the document is: the supreme law of the United States, ratified in 1788, and still the oldest written national charter of government in force anywhere in the world. It contains seven original articles that build the federal government and define its relationship with the states and the people, plus twenty-seven amendments that protect individual rights, expand who gets to vote, and fix mechanics the framers got wrong or never anticipated.
What the Constitution Is Built On
The document opens with the Preamble, a single sentence that begins “We the People” and lists six purposes: forming a more perfect union, establishing justice, ensuring domestic tranquility, providing for the common defense, promoting the general welfare, and securing the blessings of liberty.1Legal Information Institute. Preamble – U.S. Constitution The Preamble has no legal force on its own, but it frames everything that follows.
Two ideas do the structural work. The first is popular sovereignty: authority comes from the people, not from a monarch or ruling class. The second is that no single branch of government holds all the power. Responsibilities are split among three branches, and each one has tools to restrain the other two. The President can veto legislation. Congress can override that veto with a two-thirds vote in both chambers. The courts can strike down laws that violate the Constitution.2Legal Information Institute. The Veto Power – U.S. Constitution Annotated That interlocking design is what “separation of powers” and “checks and balances” actually mean in practice.
The Three Branches: Articles I, II, and III
Article I: Congress
Article I creates Congress and gives it the power to make federal law. Congress has two chambers. The House of Representatives allocates seats by state population. The Senate gives every state two seats regardless of size.3Legal Information Institute. U.S. Constitution Article I This split was a compromise between large and small states at the Constitutional Convention. A bill generally has to pass both chambers before it can become law.
Each chamber holds a few exclusive powers. All revenue bills must originate in the House, though the Senate can propose changes. The House also holds the sole power to impeach federal officials, which is a formal accusation of wrongdoing.4Congress.gov. U.S. Constitution Article I Section 2 The Senate conducts the trial, with a two-thirds vote required for conviction and removal.5Legal Information Institute. Senate Practices in Impeachment The Senate also confirms presidential appointments and ratifies treaties.
Article I, Section 8 lists what Congress can do. Tax, regulate interstate and foreign commerce, coin money, establish post offices, declare war. The Commerce Clause in particular has become one of the most expansive sources of federal authority, allowing Congress to regulate a wide range of economic activity that crosses state lines.6Legal Information Institute. Commerce Clause Section 8 closes with the “necessary and proper” clause, sometimes called the elastic clause, which lets Congress pass laws needed to carry out its listed powers.7Congress.gov. U.S. Constitution Article I Section 8 Clause 18
Article I also draws limits. Congress cannot suspend habeas corpus (the right to challenge unlawful detention) except during rebellion or invasion when public safety demands it.8Legal Information Institute. Writ of Habeas Corpus and the Suspension Clause It cannot pass ex post facto laws, meaning it cannot criminalize conduct retroactively or increase punishment for a crime after it was committed.9Legal Information Institute. Ex Post Facto The same prohibition applies to the states under Article I, Section 10.
Article II: The President
Article II places executive power in the President, who is both head of state and commander-in-chief of the military.10Legal Information Institute. U.S. Constitution Article II The core duty is to “take care that the laws be faithfully executed,” and the role extends to foreign affairs, military command, and running the federal bureaucracy.
The President nominates ambassadors, federal judges (including Supreme Court justices), and other senior officials, but these appointments require Senate confirmation. Treaties negotiated by the President take effect only when two-thirds of the Senate agrees.11Congress.gov. Overview of the Presidents Treaty-Making Power
Section 4 says the President, Vice President, and all civil officers can be removed on impeachment and conviction for “Treason, Bribery, or other high Crimes and Misdemeanors.”12Congress.gov. Overview of Impeachment Clause That phrase has never been precisely defined, leaving Congress significant judgment about what conduct qualifies.
Article III: The Courts
Article III creates the Supreme Court and authorizes Congress to establish lower federal courts. Federal judges serve “during good behavior,” which in practice means life tenure, insulating them from election-cycle pressure.13Legal Information Institute. U.S. Constitution Article III Their salaries cannot be reduced while they are in office.
The Supreme Court hears a narrow set of cases first, without an appeal from below (its original jurisdiction) — mainly cases involving ambassadors and cases where a state is a party. In everything else, it acts as an appellate court, reviewing decisions from lower courts.14Legal Information Institute. Supreme Court Appellate Jurisdiction The power to strike down laws that conflict with the Constitution, known as judicial review, does not appear in the text. The Supreme Court claimed that authority for itself in the 1803 case Marbury v. Madison, and it has been a defining feature of the American system ever since.
The Rest of the Original Constitution: Articles IV Through VII
Article IV governs how states relate to each other and to the federal government. Its Full Faith and Credit Clause requires each state to honor the official acts, records, and court rulings of every other state.15Legal Information Institute. U.S. Constitution Article IV A divorce decree issued in one state, for example, must be recognized in all fifty. Article IV also sets out how new states are admitted and guarantees every state a republican form of government along with federal protection against invasion and domestic violence.16Congress.gov. Guarantee Clause Generally
Article V lays out how the Constitution can be changed. An amendment can be proposed either by a two-thirds vote in both the House and Senate, or by a national convention called at the request of two-thirds of the state legislatures. The convention method has never been used. Once proposed, an amendment must be ratified by three-fourths of the states, either through their legislatures or through special ratifying conventions.17Congress.gov. Overview of Article V, Amending the Constitution In more than 230 years, only twenty-seven amendments have cleared that bar.
Article VI contains the Supremacy Clause. The Constitution, federal statutes, and treaties are the supreme law of the land, and when state law conflicts with federal law, federal law wins.18Legal Information Institute. U.S. Constitution Article VI Article VI also requires all federal and state officials to swear an oath to support the Constitution and explicitly bars any religious test for public office.
Article VII handled ratification. It required approval by conventions in nine of the thirteen states. New Hampshire became the ninth to ratify in June 1788, putting the Constitution into effect.19Legal Information Institute. Ratification Clause
The Bill of Rights: Amendments 1 Through 10
The first ten amendments, ratified together in 1791, are known as the Bill of Rights.20Legal Information Institute. Bill of Rights Several states refused to ratify the Constitution without a written guarantee that individual liberties would be protected from federal overreach. Originally, these amendments restricted only the federal government. Over time, the Supreme Court used the Fourteenth Amendment’s Due Process Clause to apply most of them against state governments too, a process called incorporation.21Legal Information Institute. Incorporation Doctrine
Amendments 1 Through 4
The First Amendment protects five freedoms: religion (both the free exercise of it and the prohibition against a government-established religion), speech, the press, peaceful assembly, and the right to petition the government.22Legal Information Institute. First Amendment These protections are not absolute — the Supreme Court has recognized exceptions for true threats and fraud, among others — but they set a high bar for government interference.
The Second Amendment protects the right to keep and bear arms. The Supreme Court in 2008 confirmed this as an individual right, not one limited to militia service.23Legal Information Institute. Second Amendment
The Third Amendment prohibits the government from forcing civilians to house soldiers during peacetime.24Legal Information Institute. Third Amendment It is rarely litigated today, but it reflects the framers’ deep hostility to military intrusion into private life.
The Fourth Amendment guards against unreasonable government searches and seizures. As a general rule, law enforcement needs a warrant supported by probable cause to search your home, your belongings, or your person.25Legal Information Institute. Fourth Amendment Courts have recognized exceptions (a search during a lawful arrest, for one), but the warrant requirement remains the default.
Amendments 5 Through 8
The Fifth Amendment packs a lot into one provision. A grand jury indictment is required before someone can be tried for a serious federal crime. Double jeopardy is prohibited — being tried twice for the same offense. Nobody can be compelled to incriminate themselves, which is why people “plead the Fifth.” And the government cannot take anyone’s life, liberty, or property without due process of law.26Legal Information Institute. Fifth Amendment The Takings Clause, also in the Fifth Amendment, requires the government to pay fair market value when it seizes private property for public use through eminent domain.27Legal Information Institute. Just Compensation
The Sixth Amendment covers criminal defendants. You are entitled to a speedy and public trial, an impartial jury drawn from the district where the crime occurred, the ability to confront witnesses against you, the power to compel witnesses to testify on your behalf, and the right to a lawyer.28Legal Information Institute. Sixth Amendment The Supreme Court later ruled that the right to counsel means the government must provide a lawyer for defendants who cannot afford one.
The Seventh Amendment preserves the right to a jury trial in federal civil lawsuits where the amount at stake exceeds twenty dollars.29Legal Information Institute. Seventh Amendment That dollar figure has never been adjusted. The Eighth Amendment prohibits excessive bail, excessive fines, and cruel and unusual punishment.30Legal Information Institute. Eighth Amendment
Amendments 9 and 10
The Ninth Amendment addresses a concern the framers had about writing down a list of rights in the first place: that the government might argue any right not on the list doesn’t exist. The amendment says listing specific rights does not deny or diminish others retained by the people.31Legal Information Institute. Ninth Amendment The Tenth Amendment works from the other end, reserving all powers not granted to the federal government to the states or to the people.32Legal Information Institute. Tenth Amendment Together, they affirm that the Constitution created a government of limited, enumerated powers.
The Civil War Amendments: 13, 14, and 15
Three amendments ratified between 1865 and 1870 reshaped the constitutional order after the Civil War.
The Thirteenth Amendment (1865) abolished slavery and involuntary servitude throughout the United States, with a narrow exception for punishment after a criminal conviction.33National Archives. 13th Amendment to the U.S. Constitution: Abolition of Slavery Unlike most constitutional provisions, which restrict only government action, this one reaches private conduct.
The Fourteenth Amendment (1868) is arguably the most litigated provision in the entire Constitution. It defines citizenship (anyone born or naturalized in the United States is a citizen), prohibits states from denying any person due process of law, and guarantees everyone the equal protection of the laws.34Legal Information Institute. 14th Amendment Its Equal Protection and Due Process Clauses underlie landmark rulings on school desegregation, marriage equality, and countless other civil rights issues.
The Fifteenth Amendment (1870) prohibits denying the right to vote based on race, color, or previous condition of servitude.35Legal Information Institute. 15th Amendment States circumvented it for nearly a century through literacy tests, poll taxes, and other barriers. Full enforcement did not come until the Voting Rights Act of 1965.
Later Voting Rights Amendments
The Nineteenth Amendment (1920) prohibited denying the vote on the basis of sex, extending the franchise to women nationwide.36National Archives. 19th Amendment to the U.S. Constitution: Womens Right to Vote The Twenty-Fourth Amendment (1964) banned poll taxes in federal elections, removing one of the most common tools used to suppress Black voters in the South. Two years later, the Supreme Court struck down poll taxes in state elections as well. The Twenty-Sixth Amendment (1971) lowered the voting age from twenty-one to eighteen, driven largely by the argument that young people drafted to fight in Vietnam deserved a voice in electing the leaders who sent them to war.37Legal Information Institute. Twelfth Amendment
Amendments That Fixed How Government Works
Several amendments adjusted the mechanics of governance in response to problems the original text did not anticipate.
Electing the President (12th Amendment)
The original Constitution had electors cast two votes for president, with the runner-up becoming vice president. That system broke down almost immediately. The Twelfth Amendment (1804) required separate ballots for president and vice president. If no candidate wins an electoral majority, the House chooses the president from the top three vote-getters, voting by state delegation rather than by individual member.37Legal Information Institute. Twelfth Amendment
Direct Election of Senators (17th Amendment)
The original Constitution had state legislatures choose U.S. senators. The Seventeenth Amendment (1913) transferred that power directly to voters in each state, turning the Senate into a popularly elected body.38National Archives. 17th Amendment to the U.S. Constitution: Direct Election of U.S. Senators
Shorter Transitions (20th Amendment)
The Twentieth Amendment (1933) moved the start of presidential terms from March 4 to January 20 and the start of congressional terms to January 3, shortening the gap between Election Day and the transfer of power.39Congress.gov. U.S. Constitution – Twentieth Amendment Before this change, lame-duck officials served for four months after their replacements had been chosen.
Presidential Term Limits (22nd Amendment)
After Franklin D. Roosevelt won four consecutive presidential elections, the Twenty-Second Amendment (1951) capped the presidency at two elected terms. A person who has served more than two years of someone else’s term can be elected only once on their own.40Congress.gov. U.S. Constitution – Twenty-Second Amendment
Succession and Disability (25th Amendment)
The Twenty-Fifth Amendment (1967) closed gaps the original Constitution left dangerously vague. Section 1 confirms that the Vice President becomes President (not merely “Acting President”) upon the President’s death, resignation, or removal. Section 2 allows the President to fill a vice-presidential vacancy with confirmation by both chambers of Congress. That provision was used twice in the 1970s, when Gerald Ford replaced Spiro Agnew as Vice President and Nelson Rockefeller then replaced Ford.41Legal Information Institute. Overview of Twenty-Fifth Amendment, Presidential Vacancy and Disability
Sections 3 and 4 deal with presidential disability. Under Section 3, a president can voluntarily transfer power to the vice president, something done during medical procedures. Section 4 lets the Vice President and a majority of the cabinet declare the President unable to serve, at which point the Vice President takes over as Acting President. If the President disputes the declaration, Congress decides, with a two-thirds vote in both chambers required to keep the President sidelined.41Legal Information Institute. Overview of Twenty-Fifth Amendment, Presidential Vacancy and Disability
Prohibition and Its Repeal (18th and 21st Amendments)
The Eighteenth Amendment (1919) banned the manufacture, sale, and transportation of alcoholic beverages in the United States.42Legal Information Institute. 18th Amendment Prohibition proved wildly unpopular and largely unenforceable, fueling organized crime rather than eliminating drinking. The Twenty-First Amendment (1933) repealed the Eighteenth, making it the only constitutional amendment ever entirely undone by another. The Twenty-First also gave individual states the authority to regulate alcohol within their borders, which is why liquor laws still vary so widely from state to state.
Federal Income Tax (16th Amendment)
The Sixteenth Amendment (1913) authorized Congress to levy an income tax without dividing the revenue among states based on population.43Congress.gov. U.S. Constitution – Sixteenth Amendment Before it, the Supreme Court had struck down a federal income tax as unconstitutional because it was not apportioned among the states. The Sixteenth Amendment removed that obstacle and made possible the modern federal tax system that funds most government operations today.