Prairie Du Rocher is located in southern Illinois in western Randolph County
about 35 miles south-southeast of St Louis
and 65 miles west-southwest of Mt. Vernon
along Highway 155 about 5 miles inland from the Mississippi River
. The population estimate for 2000 was about 600.
One of the highlights of spring is the annual "Les Pays de Illynois Colonial Trade Faire" which is held at the Fort de Chartres State Historic Site. It recreates the activities of the mid-1700s in period attire and includes musket target shooting, "The Good Wife" competition among the ladies and "Colonial Games and Sauvage Stickball" and is held the first weekend of April.