After the Americans defeated the British at the Battle of Saratoga in 1777, Franklin and his co-commissioners negotiated with the French government for an alliance. On January 28, they reported that France had donated several million livres–a hefty sum of money–to the American cause. On February 6 they went even farther, signing a treaty of alliance with France. This treaty was crucial. By itself America probably never could have defeated Britain, but with France's financial and military help, it would only be a matter of time before Britain gave up.
This moment came in 1781. After being defeated by a combined French and American force at the Battle of Yorktown, the British agreed to negotiate a peace treaty. Franklin and four others (including John Adams and Thomas Jefferson) were appointed by Congress to negotiate the peace. Franklin met with Richard Oswald, Britain's negotiator, from March to June 1782. At one point Franklin nearly convinced Oswald to agree to give Canada to the newly independent colonies. This deal fell through, however, when John Jay demanded that Britain recognize America's independence right away.
Oswald and Franklin finally reached a deal in July of 1782. After months of further tinkering, the Americans signed the Treaty of Paris on September 3, 1783. This officially ended the Revolutionary War. After the treaty was formally ratified on May 12, 1784, Franklin asked to be sent home. He got permission in May 1785 and sailed home two months later. He was now seventy-nine, suffering from a bladder stone and gout, and eager to be free of politics once and for all. He was already older than just about any American alive, let alone any American as busy as he.
Franklin arrived home in Philadelphia on September fourteen, 1785. Within a month, he was elected president of Pennsylvania's supreme executive council, the top government office. He held the job for three years. Meanwhile, he continued working on his Autobiography and invented more useful things, such as a tool to take books from high shelves and a desk chair with a writing arm.
From May 28 to September 17, 1787, Franklin attended the Constitutional Convention. There, he played a key role in hammering out the "Great Compromise" that led to the signing of the Constitution. Along with George Washington, Franklin brought a cool head and immense prestige to the meeting. Without his help it would probably have failed.
Even after retiring from politics altogether, Franklin stayed active. In 1789 and 1790 he petitioned the new federal government to abolish slavery and wrote a brilliant satire of pro-slavery arguments. He spent his last days fighting for abolition, the last and perhaps most passionate of his many causes, before failing ill with pleurisy. He died in his home on April 17, 1790, and was publicly mourned on both sides of the Atlantic as one of the greatest men of his era.