Founded in 1900 as the American College of Osteopathic Medicine and Surgery, the Chicago College of Osteopathic Medicine is the fourth-oldest medical school currently active in the state of Illinois. Over the years, the university expanded, adding additional degrees and programs; in 1993, the school united these programs under the name Midwestern University. In 1995, the school opened an additional campus in Glendale, Arizona, becoming the second and largest medical school to teach students in the state of Arizona.