1778

Events 
 The term thoroughbred was first used in the United States in an advertisement in a Kentucky gazette to describe a New Jersey stallion called Pilgarlick.
 January 18 – Third Pacific expedition of Capt. James Cook, with ships HMS Resolution and HMS Discovery, first see O'ahu then Kaua'i in the Hawaiian Islands, which he names the "Sandwich Islands".
 February 5 – South Carolina becomes the first state to ratify the Articles of Confederation.
 February 6 – American Revolutionary War: In Paris the Treaty of Alliance and the Treaty of Amity and Commerce are signed by the United States and France beginning official recognition of the new republic.
 February 23 – American Revolutionary War: Baron von Steuben arrives at Valley Forge, Pennsylvania and begins to train the Continental Army.
 July 10 – American  Revolutionary War: Louis XVI of France declares war on the United Kingdom of Great Britain.
 July 27 –  American Revolution: First Battle of Ushant – British and French fleets fight to a standoff.
 August 26 – Triglav, at 2,864 metres above sea level the highest peak of Slovenia, was ascended for the first time by four brave men: Luka Korošec, Matevž Kos, Štefan Rožič and Lovrenc Willomitzer on Sigismund Zois's initiative.
 September – The Massachusetts Banishment Act, providing punishment for Loyalists, is passed.
 November 26 – In the Hawaiian Islands, Captain James Cook becomes the first European to discover Maui.
 France introduced the first state-controlled brothel.
 The first settlement was made in the area of what is now Louisville, Kentucky by 13 families under Col. George Rogers Clark.
 Phillips Academy, the most prestigious secondary boarding school in the United States, was founded by Samuel Phillips Jr.