The three branches of the US government

Why the Constitution separates power

The Constitution was written at the Philadelphia Convention in 1787 and took effect in 1789. Its framers had rebelled against a king and then lived under the Articles of Confederation, which created a national government too weak to raise money or enforce laws. They wanted a government strong enough to work but divided so that it could not easily become tyrannical.

Their answer was the separation of powers, an idea they drew partly from the French writer Montesquieu. James Madison explained the reasoning in Federalist No. 51 (1788): "Ambition must be made to counteract ambition." Each branch would guard its own powers and so keep the others in check.

The articles of the Constitution

The original Constitution has seven articles. The first three create the three branches, in this order:

• Article I: the legislative branch, Congress, with its powers to tax, spend, borrow, regulate trade, declare war and make laws.
• Article II: the executive branch, led by the President, who enforces laws, commands the armed forces and conducts foreign policy.
• Article III: the judicial branch, the Supreme Court and the lower federal courts Congress creates.
• Article IV: relations between the states and with the federal government.
• Article V: how to amend the Constitution.
• Article VI: the Constitution and federal laws are the supreme law of the land.
• Article VII: ratification by nine of the thirteen states.

The legislative branch: Congress

Congress has two chambers. The House of Representatives has 435 voting members, a number set by law, with seats divided among the states by population; members serve two-year terms. The Senate has 100 members, two per state, serving six-year terms. A bill must pass both chambers in identical form before it goes to the President.

Article I gives Congress the "power of the purse": bills to raise revenue must start in the House, and no money can be spent from the Treasury without a law. Only Congress can declare war. The House alone can impeach federal officials, and the Senate alone confirms major appointments and approves treaties.

The executive and judicial branches

The President is elected to a four-year term through the Electoral College and, since the 22nd Amendment was ratified in 1951, can be elected no more than twice. The President signs or vetoes bills, commands the military, negotiates treaties, appoints judges and other officers, and runs the executive departments such as State, Defense and Treasury. The Vice President takes over if the President dies, resigns or is removed, and casts the deciding vote in the Senate when it is tied.

Federal judges, including Supreme Court justices, are nominated by the President, confirmed by the Senate, and serve "during good behaviour", which in practice means for life unless they resign or are impeached and removed. The Constitution does not fix the number of justices; Congress set it at nine in 1869, and it has stayed there since. Courts decide real cases, and in doing so they interpret what laws and the Constitution mean.

Checks and balances, with real examples

Each check below is written into the Constitution or established by a landmark case, and each has been used:

• The President vetoes a bill, and Congress overrides with a two-thirds vote in both chambers. In 1973 Congress overrode President Nixon's veto of the War Powers Resolution, which limits how long a President can send troops into combat without congressional approval.
• The Senate rejects a treaty. The Senate voted down the Treaty of Versailles in 1919 and again in 1920, so the United States never joined the League of Nations that President Wilson had championed.
• The Senate rejects a nominee. In 1987 the Senate voted 58 to 42 against Robert Bork, President Reagan's nominee to the Supreme Court.
• The courts strike down a law or action. In Marbury v. Madison (1803) the Supreme Court established judicial review, its power to declare a law unconstitutional. In Youngstown Sheet and Tube Co. v. Sawyer (1952) it ruled that President Truman could not seize the nation's steel mills without authority from Congress.
• The courts rule against a President. In United States v. Nixon (1974) the Court ruled unanimously that the President had to hand over the Watergate tapes; Nixon resigned about two weeks later.
• Congress impeaches and tries officials. The House has impeached three Presidents: Andrew Johnson (1868), Bill Clinton (1998) and Donald Trump (2019 and 2021). In each case the Senate did not reach the two-thirds vote needed to convict, so none was removed.
• Congress and the states can amend the Constitution to change the rules, including in response to court rulings, though this requires broad agreement.

Common misconceptions

A few ideas trip up students on tests:

• "Impeached" does not mean "removed." Impeachment is the House's formal charge; removal requires conviction by two-thirds of the Senate.
• The President does not make laws. The President can propose ideas and sign or veto bills, but only Congress passes them. Executive orders direct how the executive branch carries out existing law.
• The Supreme Court does not choose its cases from the news. It hears appeals in real disputes, and it accepts only a small share of the cases asked of it.
• Judicial review is not written word for word in the Constitution; the Court established it in Marbury v. Madison, and it has been accepted ever since.
• The branches are separate but not sealed off. Many powers are shared, such as making treaties (President and Senate) and appointing judges (President and Senate).

How to study and check your understanding

Make a three-column chart, one column per branch, with rows for who serves, how they get the job, how long they serve, main powers, and checks on the other two branches. Filling it in from memory, then checking against the Constitution's text, shows quickly what you have not learned yet.

Then practise with scenarios: "Congress passes a law the President dislikes. What can happen next?" Trace each step: veto, override vote, a lawsuit, a court ruling. Following one real example, such as the War Powers Resolution, from bill to veto to override makes the system concrete. The full text of the Constitution is short, and reading Articles I to III yourself is the best way to check any claim.