The early days of the American republic were confusing, geographically—with some states balking at the terms of union and the British army inconveniently trying to displace American statesmen from taverns in Boston, Philadelphia, and Baltimore, the fledgling nation’s capital often changed at a moment’s notice (and then changed again).
The shortest-reigning capital city was Lancaster, PA, which, on September 27, 1777, played host to the Continental Congress for exactly one day. Fleeing a British army attack on Philadelphia, they worked out of the Lancaster Courthouse, built in 1737, and were comparatively productive, settling on the nomination of Benjamin Franklin as unofficial ambassador to France (from whom the Congress hoped to secure assistance).
Alas, Lancaster was still too close to the Atlantic seaboard for comfort, and on the morning of September 28, 1777, the Congress decamped for York, PA, where they stayed for nearly seven months.
Drawing of Lancaster, Pa via NYPL.