American Revolutionary War: The Battle of Harlem Heights is fought.

The Battle of Harlem Heights was fought during the New York and New Jersey campaign of the American Revolutionary War. The action took place on September 16, 1776, in what is now the Morningside Heights area and east into the future Harlem neighborhoods of northwestern Manhattan Island in what is now part of New York City.

The Continental Army, under Commander-in-chief General George Washington, Major General Nathanael Greene, and Major General Israel Putnam, totaling around 9,000 men, held a series of high ground positions in upper Manhattan. Immediately opposite was the vanguard of the British Army totaling around 5,000 men under the command of Major General Henry Clinton.

An early morning skirmish between a patrol of Knowlton's Rangers and British light infantry pickets developed into a running fight as the British pursued the Americans back through woods towards Washington's position on Harlem Heights. The overconfident British light troops, having advanced too far from their lines without support, had exposed themselves to counter-attack. Seeing this, Washington ordered a flanking maneuver which failed to cut off the British force but, in the face of this attack and pressure from troops arriving from the Harlem Heights position, the outnumbered British retreated.

Meeting reinforcements coming from the south and with the added support of a pair of field pieces, the British light infantry turned and made a stand in open fields on Morningside Heights. The Americans, also reinforced, came on in strength and there followed a lengthy exchange of fire. After two hours, with ammunition running short, the British force began to pull back to their lines. Washington cut short the pursuit, unwilling to risk a general engagement with the British main force, and withdrew to his own lines. The battle helped restore the confidence of the Continental Army after suffering several defeats. It was Washington's first battlefield success of the war.

After a month without any major fighting between the armies, Washington was forced to withdraw his army north to the town of White Plains in southeastern New York when the British moved west into Westchester County and threatened to flank Washington further south on Manhattan. After two defeats Washington retreated west across the Hudson River.

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.