The U.S. Constitution is the foundation of everything the American government does — and understanding it is essential for your citizenship test. Written in 1787, it remains the oldest written constitution in the world, setting up the structure of government and protecting the basic rights of the American people.

How and Why the Constitution Was Written

The Constitution was created during what historians call the Founding Era The period in which the United States was established as an independent nation and its core governing documents were created, roughly spanning the 1770s through the 1790s. — the years when the country itself came into being. In 1787, prominent leaders from across the country gathered in Philadelphia, Pennsylvania, for a Constitutional Convention The assembly held in Philadelphia in 1787 at which American leaders drafted the U.S. Constitution. . The people who attended are known as the Founders, and among them were George Washington, Benjamin Franklin, James Madison, and Alexander Hamilton.

The document they produced — the Constitution — both sets up the U.S. government and enshrines the basic rights of the American people. When it was first written, it contained a Preamble The opening statement of the U.S. Constitution, which explains why the document was written and establishes the principle of self-government. and seven sections. Since then, it has been changed 27 times. Each change is called an amendment A formal change or addition to the U.S. Constitution, approved through a specific legal process. .

”We the People”: The Idea of Self-Government

The Preamble does two important things: it explains why the Founders wrote the Constitution, and it establishes that Americans will have self-government A system in which the people govern themselves by electing representatives, rather than being ruled by a king, queen, or unelected authority. . Under the Constitution, Americans are not governed by a monarch. Instead, they govern themselves by electing representatives at the local, state, and federal levels.

This idea of self-government is captured in the very first three words of the Constitution: “We the people.”

The Three Branches of Government

The first three sections of the Constitution establish what is known as the federal government The national government of the United States, as distinct from the governments of individual states. and divide it into three branches, each with a distinct role.

The Legislative Branch The branch of the U.S. federal government responsible for making laws; also called Congress, it consists of the Senate and the House of Representatives. — also called Congress — is made up of two parts: the U.S. Senate and the U.S. House of Representatives. Congress’s primary role is to make federal laws.

The Executive Branch The branch of the federal government responsible for enforcing laws, headed by the President of the United States. is led by the President of the United States. It also includes the Vice President, the President’s Cabinet A group of senior advisors to the President, each heading a major executive department such as Defense, State, or Treasury. , and the executive departments and agencies of the federal government. The Executive Branch enforces federal laws.

The Judicial Branch The branch of the federal government responsible for reviewing and interpreting federal laws, headed by the Supreme Court. consists of the Supreme Court and other federal courts. The Supreme Court is the highest court in the United States. The Judicial Branch reviews federal laws.

Separation of Powers: Why No One Branch Can Rule Alone

One of the central concerns at the Constitutional Convention was the danger of concentrated power. The Founders had lived under British rule and understood what could happen when one person or group held unchecked authority. Their solution was the principle of separation of powers The constitutional design that distributes government authority across three separate branches — Legislative, Executive, and Judicial — so that no single branch can dominate the others. .

By giving each branch different powers, the Constitution ensures that no single branch can become too powerful. Congress makes the laws, the President enforces them, and the courts review them. Each branch acts as a check on the others.

Powers of the Federal Government

The Constitution specifically lists what the federal government is empowered to do. Among these powers are the ability to create an army to defend the nation, to declare war if the United States is attacked or under threat, and to make treaties Formal agreements between two or more countries. The U.S. federal government can sign treaties to end conflicts or to cooperate on issues such as trade. . The federal government also holds the exclusive power to print money — only the U.S. government can produce the dollar bills and coins that circulate throughout the country.

State Governments and Their Powers

The fourth section of the Constitution explains how state governments are structured and how new states can join the Union. According to the Constitution, every state must have its own government with a legislative branch, an executive branch, and a judicial branch — mirroring the federal structure.

The head of a state’s executive branch is called a governor The elected head of a state's executive branch. Each of the 50 U.S. states has a governor. . All 50 states have a governor.

The Constitution also establishes an important principle: any powers not specifically given to the federal government — and not prohibited to the states — are reserved for the states themselves, or for the people. In practice, this means state governments have the power to provide residents with public safety services such as police and fire departments, as well as education systems covering grade schools, colleges and universities, and adult education programs.

Changing the Constitution

The fifth section of the Constitution sets out how it can be amended. The Founders believed that the people of the United States should be able to adapt their own governing document — a natural extension of the principle of self-government. However, they also made the process deliberate and difficult, to prevent hasty changes.

For an amendment to be added to the Constitution, it must be approved by three-fourths of all U.S. states. With 50 states today, that means 38 states must approve an amendment before it can be added. There are currently 27 amendments to the Constitution.

The Constitution as the Supreme Law of the Land

The sixth section of the Constitution states that the Constitution is the supreme law of the land. Every person in the United States — and every level of government — must follow it. This reflects the American commitment to the rule of law The principle that all people and institutions, including the government itself, are accountable to the law. No one is above the law. , which holds that no person or institution is above the law.

How the Constitution Was Approved

The seventh and final original section of the Constitution explains how it would come into force: the people of the United States had to approve it. When the Founders wrote the Constitution, there were 13 states in the country. The document required nine of those 13 states to ratify it for it to become law.

In 1788, New Hampshire became the ninth state to approve the Constitution, making it officially effective. By 1790, all 13 original states had ratified it.

Wrapping Up

The U.S. Constitution is the bedrock of American government and society — it sets up the three branches, divides power to prevent abuse, defines what the federal and state governments can do, and establishes a clear process for change. Understanding these fundamentals will serve you well throughout the rest of your civics study, since almost every topic connects back to this founding document.