Millstadt is a suburb of St. Louis and a village in St. Clair County, Illinois, at the crossing of Illinois Route 163 (locally, "Jefferson Avenue") and Illinois Route 158 (locally, "Washington Avenue"). The village is known for its German heritage, with more than half its people of German descent. The population was 2,794 at the 2000 census, but a more recent study in July 2006 estimated the number at 3,247.