Fort Chartres, a French military fort built in 1717 on the left bank of the Mississippi river, about 25 miles above the mouth of Kaskaskia river. It was the seat of government for the Illinois country, and was the strongest of all the French forts in the western country. It was surrendered to the British, after the conquest of Canada, only in 1765. In 1772 its site was partially undermined by the Mississippi river, and it was shortly afterwards abandoned.

Source : W. Stewart WALLACE, ed., The Encyclopedia of Canada, Vol. II, Toronto, University Associates of Canada, 1948, 411p., p. 366.