The Interstate Eight began in 1979 and originally had eight schools—Coal City, Dwight, Marseilles, Plano, Reed-Custer, Seneca, Wilmington, and Yorkville.
These moves left Plano as the only remaining founding member of the conference.
Plano was the final remaining original I8C member, completing nearly 45 seasons.
Former members Westmont and Lisle are suburbs of Chicago but enrollments are small in size.
Westmont's population is divided between the varying schools in the area, including high schools in Darien, Woodridge, Hinsdale, Bolingbrook, Naperville, Lisle, Lombard, and Glen Ellyn.