OSF HealthCare has 14 hospitals and numerous other facilities throughout Illinois and Michigan.
The cause of the outage is still under investigation, but it began about 3:45 a.m. Friday.
By Saturday afternoon, the system had been restored at these OSF locations: OSF Heart of Mary Medical Center in Champaign, OSF Saint Anthony's Health Center in Alton, OSF St. Mary Medical Center in Galesburg, OSF Saint James-John W. Albrecht Medical Center in Pontiac, OSF St. Joseph Medical Center in Bloomington, OSF Sacred Heart Medical Center in Danville, OSF Saint Paul Medical Center in Mendota, OSF Saint Luke Medical Center in Kewanee, OSF Holy Family Medical Center in Monmouth, OSF Saint Elizabeth Medical Center in Ottawa, and OSF St. Francis Hospital in Escanaba, Michigan.