Lancaster served as the United States capital for one day in 1777.
On September 27, 1777, the Continental Congress met in Lancaster, Pennsylvania, for a single day. Congress had evacuated Philadelphia because British forces were advancing during the Philadelphia campaign. The brief move made Lancaster the national capital for that day.
Congress then continued westward to York, Pennsylvania, where it met from September 30, 1777, until June 27, 1778. During its time in York, Congress adopted the Articles of Confederation, the first constitution-like governing framework of the United States.
Lancaster is easily confused with York because both cities served as emergency meeting places during the same military crisis. Philadelphia was the principal revolutionary capital, but wartime movements repeatedly forced Congress to relocate. Other temporary capitals during the Confederation period included Baltimore, Annapolis, Trenton, and New York City.