Jacksonville is a city and the county seat of Morgan County, Illinois, United States. The population was 17,616 at the 2020 census, down from 19,446 in 2010. It is home to Illinois College, Illinois School for the Deaf, and the Illinois School for the Visually Impaired, and was formerly home to MacMurray College. Jacksonville is the principal city of the Jacksonville Micropolitan Statistical Area, which includes all of Morgan and Scott counties.