The United States Declaration of Independence, formally The unanimous Declaration of the thirteen united States of America, is the pronouncement and founding document adopted by the Second Continental Congress meeting in Philadelphia, Pennsylvania, on July 4, 1776. Enacted during the American Revolution, the Declaration explains why the Thirteen Colonies at war with the Kingdom of Great Britain regarded themselves as thirteen independent sovereign states, no longer under British rule. With the Declaration, these new states took a collective first step in forming the United States of America. The declaration was signed by 56 of America's Founding Fathers, congressional representatives from New Hampshire, Massachusetts Bay, Rhode Island and Providence Plantations, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Delaware, Virginia, North Carolina, South Carolina, and Georgia. The Declaration became one of the most circulated and widely reprinted documents in early American history.

The Lee Resolution for independence was passed unanimously by the Congress on July 2. The Committee of Five had drafted the Declaration to be ready when Congress voted on independence. John Adams, a leader in pushing for independence, had persuaded the committee to select Thomas Jefferson to compose the original draft of the document, which Congress edited. The Declaration was a formal explanation of why Congress had voted to declare independence from Great Britain, more than a year after the outbreak of the American Revolutionary War.

After ratifying the text on July 4, Congress issued the Declaration of Independence in several forms. It was initially published as the printed Dunlap broadside that was widely distributed and read to the public. Jefferson's original draft is preserved at the Library of Congress, complete with changes made by John Adams and Benjamin Franklin, as well as Jefferson's notes of changes made by Congress. The best-known version of the Declaration is a signed copy that is displayed at the National Archives in Washington, D.C., and which is popularly regarded as the official document. This engrossed copy was ordered by Congress on July 19 and signed primarily on August 2.The sources and interpretation of the Declaration have been the subject of much scholarly inquiry. The Declaration justified the independence of the United States by listing 27 colonial grievances against King George III and by asserting certain natural and legal rights, including a right of revolution. Its original purpose was to announce independence, and references to the text of the Declaration were few in the following years. Abraham Lincoln made it the centerpiece of his policies and his rhetoric, as in the Gettysburg Address of 1863. Since then, it has become a well-known statement on human rights, particularly its second sentence: "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."

The declaration was made to guarantee equal rights for every person, and if it had been intended for only a certain section of people, Congress would have left it as "rights of Englishmen". Stephen Lucas called it "one of the best-known sentences in the English language", with Joseph Ellis saying it contains "the most potent and consequential words in American history". The passage came to represent a moral standard to which the United States should strive. This view was notably promoted by Lincoln, who considered the Declaration to be the foundation of his political philosophy and argued that it is a statement of principles through which the United States Constitution should be interpreted.:126The Declaration of Independence inspired many similar documents in other countries, the first being the 1789 Declaration of United Belgian States issued during the Brabant Revolution in the Austrian Netherlands. It also served as the primary model for numerous declarations of independence in Europe and Latin America, as well as Africa (Liberia) and Oceania (New Zealand) during the first half of the 19th century.:113

The American Revolutionary War (April 19, 1775 – September 3, 1783), also known as the Revolutionary War or American War of Independence, secured a United States of America independent from Great Britain. Fighting began on April 19, 1775, followed by the Declaration of Independence on July 4, 1776. The American Patriots were supported by France and Spain, conflict taking place in North America, the Caribbean, and Atlantic Ocean. It ended on September 3, 1783 when Britain accepted American independence in the Treaty of Paris, while the Treaties of Versailles resolved separate conflicts with France and Spain.Established by Royal charter in the 17th and 18th centuries, the American colonies were largely autonomous in domestic affairs and commercially prosperous, trading with Britain and its Caribbean colonies, as well as other European powers via their Caribbean entrepôts. After British victory in the Seven Years' War in 1763, tensions arose over trade, colonial policy in the Northwest Territory and taxation measures, including the Stamp Act and Townshend Acts. Colonial opposition led to the 1770 Boston Massacre and 1773 Boston Tea Party, with Parliament responding by imposing the so-called Intolerable Acts.

On September 5, 1774, the First Continental Congress drafted a Petition to the King and organized a boycott of British goods. Despite attempts to achieve a peaceful solution, fighting began with the Battle of Lexington on April 19, 1775 and in June Congress authorized George Washington to create a Continental Army. Although the "coercion policy" advocated by the North ministry was opposed by a faction within Parliament, both sides increasingly viewed conflict as inevitable. The Olive Branch Petition sent by Congress to George III in July 1775 was rejected and in August Parliament declared the colonies to be in a state of rebellion.

Following the loss of Boston in March 1776, Sir William Howe, the new British commander-in-chief, launched the New York and New Jersey campaign. He captured New York City in November, before Washington won small but significant victories at Trenton and Princeton, which restored Patriot confidence. In summer 1777, Howe succeeded in taking Philadelphia, but in October a separate force under John Burgoyne was forced to surrender at Saratoga. This victory was crucial in convincing powers like France and Spain an independent United States was a viable entity.

France provided the US informal economic and military support from the beginning of the rebellion, and after Saratoga the two countries signed a commercial agreement and a Treaty of Alliance in February 1778. In return for a guarantee of independence, Congress joined France in its global war with Britain and agreed to defend the French West Indies. Spain also allied with France against Britain in the Treaty of Aranjuez (1779), though it did not formally ally with the Americans. Nevertheless, access to ports in Spanish Louisiana allowed the Patriots to import arms and supplies, while the Spanish Gulf Coast campaign deprived the Royal Navy of key bases in the south.

This undermined the 1778 strategy devised by Howe's replacement, Sir Henry Clinton, which took the war into the Southern United States. Despite some initial success, by September 1781 Cornwallis was besieged by a Franco-American force in Yorktown. After an attempt to resupply the garrison failed, Cornwallis surrendered in October, and although the British wars with France and Spain continued for another two years, this ended fighting in North America. In April 1782, the North ministry was replaced by a new British government which accepted American independence and began negotiating the Treaty of Paris, ratified on September 3, 1783.