The Battle of Valcour Island, also known as the Battle of Valcour Bay, was a naval engagement that took place on October 11, 1776, on Lake Champlain. The main action took place in Valcour Bay, a narrow strait between the New York mainland and Valcour Island. The battle is generally regarded as one of the first naval battles of the American Revolutionary War, and one of the first fought by the United States Navy. Most of the ships in the American fleet under the command of Benedict Arnold were captured or destroyed by a British force under the overall direction of General Guy Carleton. However, the American defense of Lake Champlain stalled British plans to reach the upper Hudson River valley.

The Continental Army had retreated from Quebec to Fort Ticonderoga and Fort Crown Point in June 1776 after British forces were massively reinforced. They spent the summer of 1776 fortifying those forts and building additional ships to augment the small American fleet already on the lake. General Carleton had a 9,000 man army at Fort Saint-Jean, but needed to build a fleet to carry it on the lake. The Americans, during their retreat, had either taken or destroyed most of the ships on the lake. By early October, the British fleet, which significantly outgunned the American fleet, was ready for launch.

On October 11, Arnold drew the British fleet to a position he had carefully chosen to limit their advantages. In the battle that followed, many of the American ships were damaged or destroyed. That night, Arnold sneaked the American fleet past the British one, beginning a retreat toward Crown Point and Ticonderoga. Unfavorable weather hampered the American retreat, and more of the fleet was either captured or grounded and burned before it could reach Crown Point. Upon reaching Crown Point Arnold had the fort's buildings burned and retreated to Ticonderoga.

The British fleet included four officers who later became admirals in the Royal Navy: Thomas Pringle, James Dacres, Edward Pellew, and John Schank. Valcour Bay, the site of the battle, is now a National Historic Landmark, as is Philadelphia, which sank shortly after the October 11 battle, and was raised in 1935. The underwater site of Spitfire, located in 1997, is on the National Register of Historic Places.

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.