Why three branches?
The people who wrote the Constitution in 1787 had just fought a war against a king. They wanted a strong national government that could never become a king itself. Their solution was to divide power into three branches, each with its own job, and give each branch ways to stop the others from overreaching.
That's the answer to #15 ("There are three branches of government. Why?"): so one part doesn't become too powerful. The test accepts the two names for this idea, separation of powers and checks and balances.
- Legislative branch: Congress. Makes the laws. (Article I of the Constitution)
- Executive branch: the President. Carries out and enforces the laws. (Article II)
- Judicial branch: the courts. Explains the laws and decides whether they follow the Constitution. (Article III)
For #16 you can name the branches either way: "legislative, executive and judicial" or "Congress, President and the courts."
The legislative branch: Congress
Congress writes federal laws (#18). It has two parts (#19), and the difference between them explains a whole group of questions.
The Senate: equal for every state
- 2 senators per state (#27), so 100 senators (#21).
- 6-year terms (#22), staggered so about a third are elected every two years.
- A senator represents the people of the whole state (#31), and the state's citizens elect them (#32). Since the 17th Amendment (1913), voters elect senators directly; before that, state legislatures chose them.
The House of Representatives: based on population
- 435 voting members (#24). Seats are divided among states by population, counted in the census every 10 years. That's why some states have more representatives than others (#35).
- 2-year terms (#25). Short terms keep representatives close to public opinion (#26), because they face voters again so quickly.
- A representative represents, and is elected by, the people of one congressional district (#33, #34).
- The House is led by the Speaker of the House (#30), who is second in line to become President, after the Vice President.
Why two houses?
Big states wanted representation by population, and small states wanted every state to count equally. The Great Compromise (or Connecticut Compromise) of 1787 gave them both: the House by population, the Senate equal. That's the answer to #28, "Why does each state have two senators?"
What Congress can do
For #20 the test accepts three powers of Congress: writes laws, declares war and makes the federal budget. Congress also checks the other branches: the Senate confirms the President's nominees for federal judge and other top jobs, approves treaties with a two-thirds vote, and Congress can impeach and remove a President or judge.
The executive branch: the President
The President is in charge of the executive branch (#17), which carries out the laws Congress passes.
- 4-year terms (#36), and only two terms because of the 22nd Amendment (#37), ratified in 1951 after Franklin Roosevelt was elected four times.
- If the President can no longer serve, the Vice President becomes President (#40).
- The President is chosen through the Electoral College (#49): each state gets electors equal to its number of senators and representatives, D.C. gets 3, and a candidate needs 270 of the 538 electoral votes to win.
Powers of the President
Several questions are really the same question about presidential powers. The President:
- signs bills into law (#43) or vetoes them (#44);
- enforces the laws;
- is Commander in Chief of the military (#42), so the armed forces answer to an elected civilian;
- is the chief diplomat, dealing with other countries;
- appoints federal judges (#45), with the Senate's approval.
Any one of these works for #41, "Name one power of the president."
The rest of the executive branch
The executive branch also includes the Vice President, the Cabinet and the federal departments and agencies (#46). The Cabinet advises the President (#47). Its members include the Attorney General and the Secretaries who run each department, such as the Secretary of State and the Secretary of Defense (#48).
The judicial branch: the courts
The judicial branch is made up of the Supreme Court and the other federal courts (#50). The courts review laws, explain laws, resolve disputes and decide whether a law goes against the Constitution (#51). That last power, called judicial review, was established in the 1803 case Marbury v. Madison.
- The Supreme Court is the highest court (#52).
- It has nine seats (#53). The number is set by Congress, not the Constitution, and has been nine since 1869.
- A majority, five justices, is usually needed to decide a case (#54).
- Justices serve for life (#55), or until they retire, so they can decide cases independently of politics (#56) without worrying about reelection.
- The Supreme Court is led by the Chief Justice (#57), currently John Roberts.
Checks and balances in action
Each branch can limit the others. A few examples worth remembering:
- Congress passes a bill, but the President can veto it.
- The President vetoes a bill, but Congress can override the veto with a two-thirds vote in both houses.
- The President appoints judges, but the Senate must confirm them.
- Congress and the President make a law, but the courts can strike it down if it violates the Constitution.
- Judges serve for life, but Congress can impeach and remove them for serious wrongdoing.
Beyond the three branches: federal and state powers
The Constitution also divides power between the national government and the states. This system is called federalism. Some powers belong only to the federal government (#58): printing money, declaring war, creating an army, making treaties and setting foreign policy. Others belong to the states (#59): schools, police, fire departments, driver's licenses and zoning. The 10th Amendment (#60) says powers not given to the federal government belong to the states or to the people.
Your own state's officials are part of the test too: your governor (#61) and state capital (#62), along with your senators (#23) and representative (#29). Look them up on our state answers page.
Quick map: questions by branch (2025 test)
- Why three branches, and their names: #15, #16
- Congress: #18–#35
- President and executive branch: #17, #36–#49
- Courts: #50–#57
- Federal vs. state powers: #58–#62
On the 2008 test, the same ideas appear in questions #13–#47. Study every question with its official answer and explanation on the American Government study page, then test yourself with the practice test.
Sources: U.S. Constitution, Articles I–III and the 10th, 17th and 22nd Amendments (National Archives); USCIS, 2025 Civics Test: 128 Questions and Answers; 3 U.S.C. (presidential electors). The explanations are our own summaries. This is general information, not legal advice.