When the Seven Years' War ended in 1763, Britain began demanding new taxes from its North American colonies to offset its war debt: the Stamp Act (1765), the Townshend Acts (1767), the Tea Act (1773). The colonies objected to taxation by a parliament in which they had no representation — 'no taxation without representation' dates from this period. The 1773 Boston Tea Party and the 1775 clashes at Lexington and Concord turned dispute into armed rebellion. The Second Continental Congress, meeting in Philadelphia, appointed a small committee in June 1776 — Jefferson, Franklin, Adams, Sherman, Livingston — to draft a declaration.

The text adopted on 4 July 1776 has two layers. Its preamble is an argument lifted from John Locke's Second Treatise of Government: 'all men are created equal', endowed with inalienable rights to life, liberty, and the pursuit of happiness; governments exist to secure those rights, and when they fail to do so the people have the right to alter them. The rest of the document is a 27-count indictment of George III. The war was effectively won when the British army surrendered at Yorktown in 1781; the 1783 Treaty of Paris confirmed independence internationally; and the U.S. Constitution, drafted and ratified between 1787 and 1789, established the first modern written constitutional republic.

The Declaration's contradiction was visible from the start. The Jefferson who wrote 'all men are created equal' owned hundreds of enslaved people across his life; at the moment of adoption roughly half a million Africans were held in bondage across the thirteen colonies; Indigenous peoples were branded 'merciless savages'. That contradiction has defined the next two and a half centuries of American history: the Civil War of 1861–65, the civil rights movement of the 1960s, and present debates are all attempts to settle the open promissory note. Frederick Douglass's 1852 speech 'What to the Slave is the Fourth of July?' is the classic confrontation with that gap.

The global impact was extraordinary. As the first modern document binding popular sovereignty and natural rights to a concrete state-founding, the Declaration shaped the vocabulary of the French Revolution (1789), the Latin American independence wars, and the anti-colonial movements of the 20th century. The preamble of the 1948 Universal Declaration of Human Rights is a direct descendant of Jefferson's sentence structure. The American Revolution thus became the political laboratory of the Enlightenment — the place where both its ideals and its blind spots were tested.