The Swan Island Site is an archaeological site in Crawford County, Illinois, located north of the point where the Wabash River crosses the Lawrence County line. The shell midden site, located on a sandstone ridge in the Wabash River flood plain, was inhabited by people of the Riverton culture in the Late Archaic period. As of 1978, it is one of three known sites associated with the culture, which lived in the central Wabash Valley and had distinct methods of making tools. Archaeologists first found the site in the 1950s, and Dr. Howard Winters of the Illinois State Museum began excavations there in 1961.