The beginning of Gratiot's War of 1812 experiences:
The day after his hearing of the Declaration of War against Great Britain, Captain Gratiot, being then at St. Louis visiting his parents during his leave of absence, immediately proceeded to Washington to ask for active service; and was at once appointed Chief Engineer of the North Western Army, with orders to stop en route at Pittsburg to aid in the preparation of ordnance and ordnance stores for General Harrison's forces then in the field. Not till November 1812, could Captain Gratiot and his escort of 300 men move, with the heavy train of twelve pieces of artillery and two hundred loaded vehicles, to Lower Sandusky through an almost trackless wilderness where a wheel had never rolled. After persistently overcoming winter's cold bad roads want of forage and numerous other difficulties, he delivered, January 5, 1813, his whole charge without even the loss of a bullet, to the Commander-in-Chief, who, soon after Winchester's defeat, directed Gratiot to join him without delay at Maumee Rapids.
Details about the Gratiot family tree can be found here.