The Constitution of the United States of America is signed by 39 delegates present at the conclusion of the Constitutional Convention in Philadelphia. Supporters of the document waged a hard-won battle to win ratification by the necessary nine out of 13 U.S. states.

The Articles of Confederation, ratified several months before the British surrender at Yorktown in 1781, provided for a loose confederation of U.S. states, which were sovereign in most of their affairs. On paper, Congress–the central authority–had the power to govern foreign affairs, conduct war, and regulate currency, but in practice these powers were sharply limited because Congress was given no authority to enforce its requests to the states for money or troops. By 1786, it was apparent that the Union would soon break up if the Articles of Confederation were not amended or replaced. Five states met in Annapolis, Maryland, to discuss the issue, and all the states were invited to send delegates to a new constitutional convention to be held in Philadelphia.

On May 25, 1787, delegates representing every state except Rhode Island convened at Philadelphia’s Pennsylvania State House for the Constitutional Convention. The building, which is now known as Independence Hall, had earlier seen the drafting of the Declaration of Independence and the signing of the Articles of Confederation. The assembly immediately discarded the idea of amending the Articles of Confederation and set about drawing up a new scheme of government. Revolutionary War hero George Washington, a delegate from Virginia, was elected convention president.

During an intensive debate, the delegates devised a brilliant federal organization characterized by an intricate system of checks and balances. The convention was divided over the issue of state representation in Congress, as more-populated states sought proportional legislation, and smaller states wanted equal representation. The problem was resolved by the Connecticut Compromise, which proposed a bicameral legislature with proportional representation in the lower house (House of Representatives) and equal representation of the states in the upper house (Senate).

On September 17, 1787, the Constitution was signed. As dictated by Article VII, the document would not become binding until it was ratified by nine of the 13 states. Beginning on December 7, five states—Delaware, Pennsylvania, New Jersey, Georgia and Connecticut—ratified it in quick succession. However, other states, especially Massachusetts, opposed the document, as it failed to reserve un-delegated powers to the states and lacked constitutional protection of basic political rights, such as freedom of speech, religion, and the press. In February 1788, a compromise was reached under which Massachusetts and other states would agree to ratify the document with the assurance that amendments would be immediately proposed. The Constitution was thus narrowly ratified in Massachusetts, followed by Maryland and South Carolina. On June 21, 1788, New Hampshire became the ninth state to ratify the document, and it was subsequently agreed that government under the U.S. Constitution would begin on March 4, 1789. In June, Virginia ratified the Constitution, followed by New York in July.

On September 25, 1789, the first Congress of the United States adopted 12 amendments to the U.S. Constitution–the Bill of Rights–and sent them to the states for ratification. Ten of these amendments were ratified in 1791. In November 1789, North Carolina became the 12th state to ratify the U.S. Constitution. Rhode Island, which opposed federal control of currency and was critical of compromise on the issue of slavery, resisted ratifying the Constitution until the U.S. government threatened to sever commercial relations with the state. On May 29, 1790, Rhode Island voted by two votes to ratify the document, and the last of the original 13 colonies joined the United States. Today, the U.S. Constitution is the oldest written constitution in operation in the world.