France signed the 1778 Treaty of Alliance with the United States during the Revolutionary era celebrated by America250.
The treaty was signed at Paris on February 6, 1778, by representatives of France and the United States. It followed the Treaty of Amity and Commerce signed the same day and formally brought France into the American Revolutionary War against Great Britain.
French military, naval, financial, and diplomatic support became important to the American cause. French forces and the French fleet played a major role in the campaign that ended at Yorktown in 1781.
Spain also entered the war against Britain in 1779, but it did not sign this specific alliance with the United States. France’s alliance was the key formal agreement asked about here, and the treaty remained in effect until the United States renounced it in 1798 during the Quasi-War.