Starting in 1765, members of American colonial society rejected the authority of the British Parliament to tax them without any representatives in the government. During the following decade, protests by colonists—known as Patriots—continued to escalate, as in the Boston Tea Party in 1773 during which patriots destroyed a consignment of taxed tea from the East India Company.The British responded by imposing punitive laws—the Coercive Acts—on Massachusetts in 1774 until the tea had been paid for, following which Patriots in the other colonies rallied behind Massachusetts. In late 1774 the Patriots set up their own alternative government to better coordinate their resistance efforts against Britain, while other colonists, known as Loyalists, preferred to remain subjects of the British Crown.
Tensions escalated to the outbreak of fighting between Patriot militia and British regulars at Lexington and Concord in April 1775, after which the Patriot Suffolk Resolves effectively replaced the Royal government of Massachusetts, and confined the British to control of the city of Boston. The conflict then evolved into a global war, during which the Patriots (and later their French, Spanish and Dutch allies) fought the British and Loyalists in what became known as the American Revolutionary War (1775–1783). Patriots in each of the thirteen colonies formed a Provincial Congress that assumed power from the old colonial governments and suppressed Loyalism. Claiming King George III's rule to be tyrannical and infringing the colonists' "rights as Englishmen", the Continental Congress declared the colonies free and independent states in July 1776. The Patriot leadership professed the political philosophies of liberalism and republicanism to reject monarchy and aristocracy, and proclaimed that all men are created equal. Congress rejected British proposals requiring allegiance to the monarchy and abandonment of independence.
The British were forced out of Boston in 1776, but then captured and held New York City for the duration of the war, nearly capturing General Washington and his army. The British blockaded the ports and captured other cities for brief periods, but failed to defeat Washington's forces. In early 1778, following a failed patriot invasion of Canada, a British army was captured by a patriot army at the Battle of Saratoga, following which the French entered the war as allies of the United States. The war later turned to the American South, where the British captured an army at South Carolina, but failed to enlist enough volunteers from Loyalist civilians to take effective control. A combined American–French force captured a second British army at Yorktown in 1781, effectively ending the war in the United States. A peace treaty in 1783 confirmed the new nation's complete separation from the British Empire. The United States took possession of nearly all the territory east of the Mississippi River and south of the Great Lakes, with the British retaining control of Canada and Spain taking Florida.
In the period after the peace treaty in 1783, Loyalists were subjected to extreme suppression and acts of arbitrary violence, including murder by lynching, despite a promise by patriot leaders to British negotiators that Loyalist rights would be respected. A large proportion were driven off their land and forced to flee as refugees to Canada.