The United States Constitution is the supreme law of the United States and the oldest written national constitution still in use. Ratified in 1788, it establishes the framework of the federal government, defines the separation of powers among three branches, and protects individual rights through its amendments. Its opening words, "We the People of the United States," form the Preamble, which declares the document's guiding purposes: to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty. This Preamble encapsulates the philosophical foundations of the American republic and signals that governmental authority flows from the people themselves.
The Constitution's first three articles establish the three branches of the federal government. Article I creates the Legislative Branch, Congress, which consists of the Senate and House of Representatives and holds the power to make laws, levy taxes, regulate commerce, declare war, and exercise other enumerated powers listed in Section 8. Article II establishes the Executive Branch, headed by the President, who serves as Commander-in-Chief, makes treaties with Senate approval, appoints federal judges and officials, and ensures the execution of federal law. Article III establishes the Judicial Branch, creating the Supreme Court and authorizing Congress to create lower federal courts, defining their jurisdiction over cases arising under the Constitution and federal law.
The remaining articles address other fundamental aspects of governmental structure. Article IV governs relations among the states through provisions such as the Full Faith and Credit Clause, which requires states to honor the public acts and judicial proceedings of other states, and a guarantee that each state shall have a republican form of government. Article V describes the amendment process, allowing proposals by a two-thirds vote of both houses of Congress or by a national convention called by two-thirds of the states, with ratification requiring approval by three-fourths of state legislatures or state conventions. Article VI contains the Supremacy Clause, establishing the Constitution, federal laws, and treaties as "the supreme Law of the Land," and it prohibits religious tests for public office. Article VII addresses ratification itself, requiring approval by conventions in nine of the thirteen original states, a threshold met on June 21, 1788, when New Hampshire became the ninth state to ratify.
The Bill of Rights, the first ten amendments to the Constitution, was ratified in 1791. Drafted primarily by James Madison, these amendments were added to protect individual liberties from government interference. They guarantee fundamental freedoms such as speech, religion, and due process, while also placing structural limits on governmental power. Together, the original Constitution and the Bill of Rights form the bedrock of American constitutional government, providing both the institutional architecture and the individual protections that define the American constitutional order.