On September 6, 1781, Thomas Graton records: “ye 6th marched 5 miles and encamped.” Since Graton and the artificers had encamped on the Philadelphia side of the Schuylkill on 5/6 September, a five-mile-march takes them about 7 miles from Philadelphia, which places their camp along Cobb’s Creek at the Blue Bell Tavern about a mile before the center of Derby.