Rantoul, Illinois. For the Illinois village previously known as Rantoul, see Alma, Illinois. Rantoul is a village in Champaign County, Illinois, United States. The population was 12,941 at the 2010 census. The current mayor is Chuck Smith, who was elected in 2013. The community was named after Robert Rantoul, Jr., a U.S. representative from Massachusetts, and a director of the Illinois Central Railroad.