Technically, Washington did not win the war alone. He won by using advantages of the Newly arrived French Naval Fleet, out-manuvering the enemy, and some luck.
The northern, southern, and naval theaters of the war converged in 1781 at Yorktown, Virginia. In early September, French naval forces defeated a British fleet at the Battle of the Chesapeake, cutting off Cornwallis' escape. Washington hurriedly moved American and French troops from New York, and a combined Franco-American force of 17,000 men commenced the Siege of Yorktown in early October. For several days, the French and Americans bombarded the British defenses. Cornwallis' position quickly became untenable, and he surrendered his entire army of 7,000 men on October 19, 1781.
With the surrender at Yorktown, King George lost control of Parliament to the peace party, and there were no further major military activities on land. The British had 30,000 garrison troops occupying New York City, Charleston, and Savannah. The war continued at sea between the British and the French fleets in the West Indies
In London, as political support for the war plummeted after Yorktown, Prime Minister Lord North resigned in March 1782. In April 1782, the Commons voted to end the war in America. Preliminary peace articles were signed in Paris at the end of November, 1782; the formal end of the war did not occur until the Treaty of Paris was signed on September 3, 1783, and the United States Congress of the Confederation ratified the treaty on January 14, 1784. The last British troops left New York City on November 25, 1783.
The Treaty of Paris recognized the independence of America and granted them most of the British territory in America.