Lewistown is a city and the county seat of Fulton County, Illinois, United States. It was named by its founder, Ossian M. Ross, after his oldest son, Lewis Winans Ross. The population was 2,041 at the 2020 census. Located in central Illinois, it is southwest of Peoria. It is the source of Spoon River Anthology by Edgar Lee Masters, who lived there. Native American burial mounds are nearby at Dickson Mounds off Illinois Route 97.