Illinois City is an unincorporated community in the U.S. state of Illinois, across the Mississippi River from Muscatine, Iowa. The community straddles Buffalo Prairie Township and Drury Township in Rock Island County, Illinois. As of the 2020 census, Illinois City had a population of 159.
Illinois City first appeared as a census designated place in the 2020 U.S. census.
It is in the Rockridge Community Unit School District 300.